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Gharakhanyan V, Wirth LJ, Garrido Torres JA, Eisenberg E, Wang T, Trinkle DR, Chatterjee S, Urban A. Discovering melting temperature prediction models of inorganic solids by combining supervised and unsupervised learning. J Chem Phys 2024; 160:204112. [PMID: 38804486 DOI: 10.1063/5.0207033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Accepted: 04/29/2024] [Indexed: 05/29/2024] Open
Abstract
The melting temperature is important for materials design because of its relationship with thermal stability, synthesis, and processing conditions. Current empirical and computational melting point estimation techniques are limited in scope, computational feasibility, or interpretability. We report the development of a machine learning methodology for predicting melting temperatures of binary ionic solid materials. We evaluated different machine-learning models trained on a dataset of the melting points of 476 non-metallic crystalline binary compounds using materials embeddings constructed from elemental properties and density-functional theory calculations as model inputs. A direct supervised-learning approach yields a mean absolute error of around 180 K but suffers from low interpretability. We find that the fidelity of predictions can further be improved by introducing an additional unsupervised-learning step that first classifies the materials before the melting-point regression. Not only does this two-step model exhibit improved accuracy, but the approach also provides a level of interpretability with insights into feature importance and different types of melting that depend on the specific atomic bonding inside a material. Motivated by this finding, we used a symbolic learning approach to find interpretable physical models for the melting temperature, which recovered the best-performing features from both prior models and provided additional interpretability.
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Affiliation(s)
- Vahe Gharakhanyan
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
- Columbia Electrochemical Energy Center, Columbia University, New York, New York 10027, USA
| | - Luke J Wirth
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Jose A Garrido Torres
- Department of Chemical Engineering, Columbia University, New York, New York 10027, USA
| | - Ethan Eisenberg
- Department of Chemical Engineering, Columbia University, New York, New York 10027, USA
| | - Ting Wang
- Department of Chemical Engineering, Columbia University, New York, New York 10027, USA
| | - Dallas R Trinkle
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA
| | | | - Alexander Urban
- Columbia Electrochemical Energy Center, Columbia University, New York, New York 10027, USA
- Department of Chemical Engineering, Columbia University, New York, New York 10027, USA
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Li WG, Liu ZT, Liu QJ. A Method for Predicting the Melting Temperature of Ionic Compounds. J Phys Chem A 2024; 128:3468-3474. [PMID: 38635347 DOI: 10.1021/acs.jpca.4c01561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
Predicting the melting temperature of materials has always been a topic of great concern. This article proposes an alternative model for determining the melting temperature of materials based on the main idea of the Lindemann melting criterion combined with the first-principles calculations of density functional theory. To verify the accuracy of the melting model, this article selected typical ionic crystals of MgO and 10 alkali metal halides as the validation objects. The calculation results indicate that the melting temperature of the MgO crystals and I-VII compounds is in good agreement with the experimental results.
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Affiliation(s)
- Wen-Guang Li
- Bond and Band Engineering Group, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, People's Republic of China
| | - Zheng-Tang Liu
- State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
| | - Qi-Jun Liu
- Bond and Band Engineering Group, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, People's Republic of China
- College of Physics, Chongqing University, Chongqing 400044, People's Republic of China
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Hirai H. Practical application of quantum neural network to materials informatics. Sci Rep 2024; 14:8583. [PMID: 38615092 PMCID: PMC11016107 DOI: 10.1038/s41598-024-59276-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 04/09/2024] [Indexed: 04/15/2024] Open
Abstract
Quantum neural network (QNN) models have received increasing attention owing to their strong expressibility and resistance to overfitting. It is particularly useful when the size of the training data is small, making it a good fit for materials informatics (MI) problems. However, there are only a few examples of the application of QNN to multivariate regression models, and little is known about how these models are constructed. This study aims to construct a QNN model to predict the melting points of metal oxides as an example of a multivariate regression task for the MI problem. Different architectures (encoding methods and entangler arrangements) are explored to create an effective QNN model. Shallow-depth ansatzs could achieve sufficient expressibility using sufficiently entangled circuits. The "linear" entangler was adequate for providing the necessary entanglement. The expressibility of the QNN model could be further improved by increasing the circuit width. The generalization performance could also be improved, outperforming the classical NN model. No overfitting was observed in the QNN models with a well-designed encoder. These findings suggest that QNN can be a useful tool for MI.
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Affiliation(s)
- Hirotoshi Hirai
- Toyota Central R&D Labs., Inc., 41-1, Yokomichi, Nagakute, Aichi, 480-1192, Japan.
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Melting temperature prediction using a graph neural network model: From ancient minerals to new materials. Proc Natl Acad Sci U S A 2022; 119:e2209630119. [PMID: 36044552 PMCID: PMC9457469 DOI: 10.1073/pnas.2209630119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The melting point is a fundamental property that is time-consuming to measure or compute, thus hindering high-throughput analyses of melting relations and phase diagrams over large sets of candidate compounds. To address this, we build a machine learning model, trained on a database of ∼10,000 compounds, that can predict the melting temperature in a fraction of a second. The model, made publicly available online, features graph neural network and residual neural network architectures. We demonstrate the model's usefulness in diverse applications. For the purpose of materials design and discovery, we show that it can quickly discover novel multicomponent materials with high melting points. These predictions are confirmed by density functional theory calculations and experimentally validated. In an application to planetary science and geology, we employ the model to analyze the melting temperatures of ∼4,800 minerals to uncover correlations relevant to the study of mineral evolution.
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Jinnouchi R, Karsai F, Verdi C, Kresse G. First-principles hydration free energies of oxygenated species at water-platinum interfaces. J Chem Phys 2021; 154:094107. [PMID: 33685177 DOI: 10.1063/5.0036097] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hydration free energy of atoms and molecules adsorbed at liquid-solid interfaces strongly influences the stability and reactivity of solid surfaces. However, its evaluation is challenging in both experiments and theories. In this work, a machine learning aided molecular dynamics method is proposed and applied to oxygen atoms and hydroxyl groups adsorbed on Pt(111) and Pt(100) surfaces in water. The proposed method adopts thermodynamic integration with respect to a coupling parameter specifying a path from well-defined non-interacting species to the fully interacting ones. The atomistic interactions are described by a machine-learned inter-atomic potential trained on first-principles data. The free energy calculated by the machine-learned potential is further corrected by using thermodynamic perturbation theory to provide the first-principles free energy. The calculated hydration free energies indicate that only the hydroxyl group adsorbed on the Pt(111) surface attains a hydration stabilization. The observed trend is attributed to differences in the adsorption site and surface morphology.
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Affiliation(s)
| | - Ferenc Karsai
- VASP Software GmbH, Sensengasse 8/16, 1090 Vienna, Austria
| | - Carla Verdi
- Computational Materials Physics, Faculty of Physics, University of Vienna, Sensengasse 8/12, 1090 Vienna, Austria
| | - Georg Kresse
- VASP Software GmbH, Sensengasse 8/16, 1090 Vienna, Austria
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Shi Y, Liu M, Wang J, Ma H, Li R, Chen Y, Mo W, Li D, Bai B, Wang X, Fa T, Chen XQ. Localized Nb clusters in U-Nb liquid alloys: An ab initio molecular dynamics study. NUCLEAR MATERIALS AND ENERGY 2021. [DOI: 10.1016/j.nme.2021.100915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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7
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Mewes JM, Smits OR. Accurate elemental boiling points from first principles. Phys Chem Chem Phys 2020; 22:24041-24050. [PMID: 33078780 DOI: 10.1039/d0cp02884c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The normal boiling point (NBP) is a fundamental property of liquids and marks the intersection of the Gibbs energies of the liquid and the gas-phase at ambient pressure. This work provides the first comprehensive demonstration of the calculation of boiling points of atomic liquids through first-principles molecular-dynamics simulations. To this end, thermodynamic integration (TDI) and perturbation theory (TPT) are combined with a density-functional theory (DFT) Hamiltonian, which provides absolute Gibbs energies, internal energies, and entropies of atomic liquids with an accuracy of a few meV/atom. Linear extrapolation to the intersection with the Gibbs energy of a non-interacting gas-phase eventually pins-down the NBPs. While these direct results can already be quite accurate, they are susceptible to a systematic over or underbinding of the employed density functional. It is shown how this dependency can be strongly reduced and the robustness of the method increased through a simple linear correction termed λ-scaling. Eventually, by carefully tuning of the technical parameters of the approach, the walltime per element is reduced from weeks to about a day (10-20k core-hours), enabling extensive testing for B, Al, Na, K, Ca, Sr, Ba, Mn, Cu, Xe, and Hg. This comprehensive benchmark demonstrates the excellent performance and robustness of the approach with a mean absolute deviation (MAD) of less than 2% from experimental NBPs and very similar accuracy for liquid entropies (MAD 2.3 J (mol K)-1, 2% relative). In some cases, the uncertainties in the predictions are several times smaller than the variation between literature values, allowing us to clear out long-standing ambiguities in the NBPs of B and Ba.
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Affiliation(s)
- Jan-Michael Mewes
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115 Bonn, Germany. and Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University Auckland, 0632 Auckland, New Zealand
| | - Odile R Smits
- Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University Auckland, 0632 Auckland, New Zealand
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8
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Miao L, Wang LW. Liquid to crystal Si growth simulation using machine learning force field. J Chem Phys 2020; 153:074501. [DOI: 10.1063/5.0011163] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Affiliation(s)
- Ling Miao
- School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, People’s Republic of China
| | - Lin-Wang Wang
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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Remsing RC, Klein ML. Molecular Simulation of Covalent Bond Dynamics in Liquid Silicon. J Phys Chem B 2020; 124:3180-3185. [PMID: 32216375 DOI: 10.1021/acs.jpcb.0c01798] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Many atomic liquids can form transient covalent bonds reminiscent of those in the corresponding solid states. These directional interactions dictate many important properties of the liquid state, necessitating a quantitative, atomic-scale understanding of bonding in these complex systems. A prototypical example is liquid silicon, wherein transient covalent bonds give rise to local tetrahedral order and consequent nontrivial effects on liquid-state thermodynamics and dynamics. To further understand covalent bonding in liquid silicon, and similar liquids, we present an ab initio-simulation-based approach for quantifying the structure and dynamics of covalent bonds in condensed phases. Through the examination of structural correlations among silicon nuclei and maximally localized Wannier function centers, we develop a geometric criterion for covalent bonds in liquid Si. We use this to monitor the dynamics of transient covalent bonding in the liquid state and estimate a covalent bond lifetime. We compare covalent bond dynamics to other processes in liquid Si and similar liquids and suggest experiments to measure the covalent bond lifetime.
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Affiliation(s)
- Richard C Remsing
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Michael L Klein
- Institute for Computational Molecular Science and Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
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10
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Machine learning provides realistic model of complex phase transition. Proc Natl Acad Sci U S A 2019; 116:10204-10205. [PMID: 31068465 DOI: 10.1073/pnas.1905457116] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Luo J, Alateeqi A, Liu L, Sinno T. Carbon solubility in liquid silicon: A computational analysis across empirical potentials. J Chem Phys 2019; 150:144503. [PMID: 30981227 DOI: 10.1063/1.5088495] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The nucleation and growth of SiC precipitates in liquid silicon is important in the crystallization of silicon used for the photovoltaic industry. These processes depend strongly on the carbon concentration as well as the equilibrium solubility relative to the precipitate phase. Here, using a suite of statistical thermodynamic techniques, we calculate the solubility of carbon atoms in liquid silicon relative to the β-SiC phase. We employ several available empirical potentials to assess whether these potentials may reasonably be used to computationally analyze SiC precipitation. We find that some of the Tersoff-type potentials provide an excellent picture for carbon solubility in liquid silicon but, because of their severe silicon melting point overestimation, are limited to high temperatures where the carbon solubility is several percent, a value that is irrelevant for typical solidification conditions. Based on chemical potential calculations for pure silicon, we suggest that this well-known issue is confined to the description of the liquid phase and demonstrate that some recent potential models for silicon might address this weakness while preserving the excellent description of the carbon-silicon interaction found in the existing models.
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Affiliation(s)
- Jinping Luo
- School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Abdullah Alateeqi
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Lijun Liu
- School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China
| | - Talid Sinno
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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12
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Bonati L, Parrinello M. Silicon Liquid Structure and Crystal Nucleation from Ab Initio Deep Metadynamics. PHYSICAL REVIEW LETTERS 2018; 121:265701. [PMID: 30636123 DOI: 10.1103/physrevlett.121.265701] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Indexed: 06/09/2023]
Abstract
Studying the crystallization process of silicon is a challenging task since empirical potentials are not able to reproduce well the properties of both a semiconducting solid and metallic liquid. On the other hand, nucleation is a rare event that occurs in much longer timescales than those achievable by ab initio molecular dynamics. To address this problem, we train a deep neural network potential based on a set of data generated by metadynamics simulations using a classical potential. We show how this is an effective way to collect all the relevant data for the process of interest. In order to efficiently drive the crystallization process, we introduce a new collective variable based on the Debye structure factor. We are able to encode the long-range order information in a local variable which is better suited to describe the nucleation dynamics. The reference energies are then calculated using the strongly constrained and appropriately normed (SCAN) exchange-correlation functional, which is able to get a better description of the bonding complexity of the Si phase diagram. Finally, we recover the free energy surface with a density functional theory accuracy, and we compute the thermodynamics properties near the melting point, obtaining a good agreement with experimental data. In addition, we study the early stages of the crystallization process, unveiling features of the nucleation mechanism.
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Affiliation(s)
- Luigi Bonati
- Department of Physics, ETH Zurich, c/o Università della Svizzera italiana, Via Giuseppe Buffi 13, CH-6900, Lugano, Switzerland
- Facoltà di Informatica, Instituto di Scienze Computazionali, National Center for Computational Design and Discovery of Novel Materials (MARVEL), Università della Svizzera italiana, Via Giuseppe Buffi 13, CH-6900, Lugano, Switzerland
| | - Michele Parrinello
- Facoltà di Informatica, Instituto di Scienze Computazionali, National Center for Computational Design and Discovery of Novel Materials (MARVEL), Università della Svizzera italiana, Via Giuseppe Buffi 13, CH-6900, Lugano, Switzerland
- Department of Chemistry and Applied Biosciences, ETH Zurich, c/o Università della Svizzera italiana, Via Giuseppe Buffi 13, CH-6900, Lugano, Switzerland
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13
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Dorner F, Sukurma Z, Dellago C, Kresse G. Melting Si: Beyond Density Functional Theory. PHYSICAL REVIEW LETTERS 2018; 121:195701. [PMID: 30468598 DOI: 10.1103/physrevlett.121.195701] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Indexed: 06/09/2023]
Abstract
The melting point of silicon in the cubic diamond phase is calculated using the random phase approximation (RPA). The RPA includes exact exchange as well as an approximate treatment of local as well as nonlocal many body correlation effects of the electrons. We predict a melting temperature of about 1735 and 1640 K without and with core polarization effects, respectively. Both values are within 3% of the experimental melting temperature of 1687 K. In comparison, the commonly used gradient approximation to density functional theory predicts a melting point that is 200 K too low, and hybrid functionals overestimate the melting point by 150 K. We correlate the predicted melting point with the energy difference between cubic diamond and the beta-tin phase of silicon, establishing that this energy difference is an important benchmark for the development of approximate functionals. The current results demonstrate that the RPA can be used to predict accurate finite temperature properties and underlines the excellent predictive properties of the RPA for condensed matter.
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Affiliation(s)
- Florian Dorner
- University of Vienna, Faculty of Physics and Center for Computational Materials Sciences, Sensengasse 8/12, 1090 Wien, Austria
| | - Zoran Sukurma
- University of Vienna, Faculty of Physics and Center for Computational Materials Sciences, Sensengasse 8/12, 1090 Wien, Austria
| | - Christoph Dellago
- University of Vienna, Faculty of Physics and Center for Computational Materials Sciences, Sensengasse 8/12, 1090 Wien, Austria
| | - Georg Kresse
- University of Vienna, Faculty of Physics and Center for Computational Materials Sciences, Sensengasse 8/12, 1090 Wien, Austria
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Taniuchi T, Tsuchiya T. The melting points of MgO up to 4 TPa predicted based on ab initio thermodynamic integration molecular dynamics. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:114003. [PMID: 29393072 DOI: 10.1088/1361-648x/aaac96] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The melting curve of MgO is extended up to 4 TPa, corresponding to the Jovian core pressure, based on the one-step thermodynamic integration method implemented on ab initio molecular dynamics. The calculated melting temperatures are 3100 and 16 000 K at 0 and 500 GPa, respectively, which are consistent with previous experimental results, and 20 600 K at 3900 GPa, which is inconsistent with a recent experimental extrapolation, which implies the molten Jovian core. A quite small Clapeyron slope ([Formula: see text]) of [Formula: see text] is found at 3900 GPa due to comparable densities of the liquid and B2 phases under extreme compression. The Mg-O coordination number in the liquid phase is saturated at around 7.5 above 1 TPa and remains smaller than that in the B2 phase (8) even at 4 TPa, suggesting no density crossover between liquid and crystal and thus no further denser crystalline phases. Dynamical properties (atomic diffusivity and viscosity) are also investigated along the melting curve to understand these behaviors in greater detail.
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Affiliation(s)
- Takashi Taniuchi
- Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
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Chavoshi SZ, Xu S, Goel S. Addressing the discrepancy of finding the equilibrium melting point of silicon using molecular dynamics simulations. Proc Math Phys Eng Sci 2017; 473:20170084. [PMID: 28690411 DOI: 10.1098/rspa.2017.0084] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Accepted: 05/05/2017] [Indexed: 11/12/2022] Open
Abstract
We performed molecular dynamics simulations to study the equilibrium melting point of silicon using (i) the solid-liquid coexistence method and (ii) the Gibbs free energy technique, and compared our novel results with the previously published results obtained from the Monte Carlo (MC) void-nucleated melting method based on the Tersoff-ARK interatomic potential (Agrawal et al. Phys. Rev. B72, 125206. (doi:10.1103/PhysRevB.72.125206)). Considerable discrepancy was observed (approx. 20%) between the former two methods and the MC void-nucleated melting result, leading us to question the applicability of the empirical MC void-nucleated melting method to study a wide range of atomic and molecular systems. A wider impact of the study is that it highlights the bottleneck of the Tersoff-ARK potential in correctly estimating the melting point of silicon.
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Affiliation(s)
- Saeed Zare Chavoshi
- Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK
| | - Shuozhi Xu
- GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA
| | - Saurav Goel
- School of Aerospace, Transport and Manufacturing, Cranfield University, Cranfield MK43 0AL, UK
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16
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Car–Parrinello molecular dynamics study of the melting behaviors of n -atom (n=6,10) graphene quantum dots. Chem Phys Lett 2017. [DOI: 10.1016/j.cplett.2017.04.058] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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17
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Meyer ER, Ticknor C, Kress JD, Collins LA. Alternative first-principles calculation of entropy for liquids. Phys Rev E 2016; 93:042119. [PMID: 27176266 DOI: 10.1103/physreve.93.042119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Indexed: 11/07/2022]
Abstract
We present an alternative method for interpreting the velocity autocorrelation function (VACF) of a fluid with application to extracting the entropy in a manner similar to the methods developed by Lin et al. [J. Chem. Phys. 119, 11792 (2003)]JCPSA60021-960610.1063/1.1624057 and improved upon by Desjarlais [Phys. Rev. E 88, 062145 (2013)]PLEEE81539-375510.1103/PhysRevE.88.062145. The liquid VACF is decomposed into two components, one gas and one solid, and each contribution's entropic portion is calculated. However, we fit both the gas and solid portions of the VACF in the time domain. This approach is applied to a single-component liquid (a two-phase model of liquid Al at the melt line) and two different two-component systems: a superionic-to-superionic (bcc to fcc) phase transition in H_{2}O at high temperatures and pressures and a metastable liquid state of MgO. For all three examples, comparisons to existing results in the literature demonstrate the validity of our alternative.
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Affiliation(s)
- Edmund R Meyer
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Christopher Ticknor
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Joel D Kress
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Lee A Collins
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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18
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Feng Y, Chen J, Alfè D, Li XZ, Wang E. Nuclear quantum effects on the high pressure melting of dense lithium. J Chem Phys 2015; 142:064506. [DOI: 10.1063/1.4907752] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Affiliation(s)
- Yexin Feng
- International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871, People’s Republic of China
| | - Ji Chen
- International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871, People’s Republic of China
| | - Dario Alfè
- London Centre for Nanotechnology, UCL, London WC1H 0AH, United Kingdom; Department of Physics and Astronomy, University College London, London WC1E6BT, United Kingdom; and Department of Earth Sciences, University College London, London WC1E6BT, United Kingdom
| | - Xin-Zheng Li
- International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871, People’s Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People’s Republic of China
| | - Enge Wang
- International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871, People’s Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People’s Republic of China
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Chen M, Hung L, Huang C, Xia J, Carter EA. The melting point of lithium: an orbital-free first-principles molecular dynamics study. Mol Phys 2013. [DOI: 10.1080/00268976.2013.828379] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Desjarlais MP. First-principles calculation of entropy for liquid metals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:062145. [PMID: 24483423 DOI: 10.1103/physreve.88.062145] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Indexed: 06/03/2023]
Abstract
We demonstrate the accurate calculation of entropies and free energies for a variety of liquid metals using an extension of the two-phase thermodynamic (2PT) model based on a decomposition of the velocity autocorrelation function into gas-like (hard sphere) and solid-like (harmonic) subsystems. The hard sphere model for the gas-like component is shown to give systematically high entropies for liquid metals as a direct result of the unphysical Lorentzian high-frequency tail. Using a memory function framework we derive a generally applicable velocity autocorrelation and frequency spectrum for the diffusive component which recovers the low-frequency (long-time) behavior of the hard sphere model while providing for realistic short-time coherence and high-frequency tails to the spectrum. This approach provides a significant increase in the accuracy of the calculated entropies for liquid metals and is compared to ambient pressure data for liquid sodium, aluminum, gallium, tin, and iron. The use of this method for the determination of melt boundaries is demonstrated with a calculation of the high-pressure bcc melt boundary for sodium. With the significantly improved accuracy available with the memory function treatment for softer interatomic potentials, the 2PT model for entropy calculations should find broader application in high energy density science, warm dense matter, planetary science, geophysics, and material science.
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Hong QJ, van de Walle A. Solid-liquid coexistence in small systems: A statistical method to calculate melting temperatures. J Chem Phys 2013; 139:094114. [DOI: 10.1063/1.4819792] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
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Hong QJ, van de Walle A. Direct first-principles chemical potential calculations of liquids. J Chem Phys 2013; 137:094114. [PMID: 22957562 DOI: 10.1063/1.4749287] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We propose a scheme that drastically improves the efficiency of Widom's particle insertion method by efficiently sampling cavities while calculating the integrals providing the chemical potentials of a physical system. This idea enables us to calculate chemical potentials of liquids directly from first-principles without the help of any reference system, which is necessary in the commonly used thermodynamic integration method. As an example, we apply our scheme, combined with the density functional formalism, to the calculation of the chemical potential of liquid copper. The calculated chemical potential is further used to locate the melting temperature. The calculated results closely agree with experiments.
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Affiliation(s)
- Qi-Jun Hong
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
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23
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Abstract
AbstractThe contemporary status of experimental as well as theoretical advances within the special view of structural phase transitions is reviewed. A brief outline of phase transitions and its classification is presented first. High-pressure experimental techniques developed for studying the structural phase transitions and elastic properties are reviewed. The complete set of theoretical and experimental data obtained is for the group II–IV alkaline earth chalcogenides. Here the authors review the currently used calculations and high-pressure behavior of these materials and the theoretical work that has been done on them.
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24
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Dozhdikov VS, Basharin AY, Levashov PR. Two-phase simulation of the crystalline silicon melting line at pressures from –1 to 3 GPa. J Chem Phys 2012; 137:054502. [PMID: 22894359 DOI: 10.1063/1.4739085] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- V S Dozhdikov
- Joint Institute for High Temperatures RAS, Izhorskaya 13 bldg. 2, Moscow 125412, Russia
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25
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Morishita T. Compressed exponential relaxation in liquid silicon: Universal feature of the crossover from ballistic to diffusive behavior in single-particle dynamics. J Chem Phys 2012; 137:024510. [DOI: 10.1063/1.4730613] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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26
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de Koker N. Melting of cubic boron nitride at extreme pressures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:055401. [PMID: 22251624 DOI: 10.1088/0953-8984/24/5/055401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Due to its large pressure range of stability and inert nature, cubic boron nitride has been proposed as a potential pressure standard for high pressure experiments. It is extremely refractive upon compression, although its melting temperature is not known beyond 10 GPa. We apply first-principles molecular dynamics to evaluate the thermodynamics of zincblende structured (cubic) and liquid boron nitride at extreme temperatures and pressures, and compute the melting curve up to 1 TPa by integration of the Clapeyron equation. The resulting equations of state reveal that liquid boron nitride becomes denser than the solid phase at pressures of around 0.5 TPa. This is expressed as a turnover in the melting curve, which reaches a maximum at 510 GPa and 6550 ± 700 K. The origin of this density crossover is explained in terms of the underlying liquid structure, which diverges from that of the zincblende structured solid as the phases are compressed.
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Affiliation(s)
- Nico de Koker
- Bayerisches Geoinstitut, Universität Bayreuth, Germany.
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27
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Wang LG, van de Walle A. Ab initio calculations of the melting temperatures of refractory bcc metals. Phys Chem Chem Phys 2012; 14:1529-34. [DOI: 10.1039/c1cp23036k] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Alfè D, Cazorla C, Gillan MJ. The kinetics of homogeneous melting beyond the limit of superheating. J Chem Phys 2011; 135:024102. [PMID: 21766920 DOI: 10.1063/1.3605601] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Molecular dynamics simulation is used to study the time-scales involved in the homogeneous melting of a superheated crystal. The interaction model used is an embedded-atom model for Fe developed in previous work, and the melting process is simulated in the microcanonical (N, V, E) ensemble. We study periodically repeated systems containing from 96 to 7776 atoms, and the initial system is always the perfect crystal without free surfaces or other defects. For each chosen total energy E and number of atoms N, we perform several hundred statistically independent simulations, with each simulation lasting for between 500 ps and 10 ns, in order to gather statistics for the waiting time τ(w) before melting occurs. We find that the probability distribution of τ(w) is roughly exponential, and that the mean value <τ(w)> depends strongly on the excess of the initial steady temperature of the crystal above the superheating limit identified by other researchers. The mean <τ(w)> also depends strongly on system size in a way that we have quantified. For very small systems of ~100 atoms, we observe a persistent alternation between the solid and liquid states, and we explain why this happens. Our results allow us to draw conclusions about the reliability of the recently proposed Z method for determining the melting properties of simulated materials and to suggest ways of correcting for the errors of the method.
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Affiliation(s)
- D Alfè
- Thomas Young Centre at UCL, London WC1E 6BT, United Kingdom.
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29
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Kirchner B, di Dio PJ, Hutter J. Real-world predictions from ab initio molecular dynamics simulations. Top Curr Chem (Cham) 2011; 307:109-53. [PMID: 21842358 DOI: 10.1007/128_2011_195] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
In this review we present the techniques of ab initio molecular dynamics simulation improved to its current stage where the analysis of existing processes and the prediction of further chemical features and real-world processes are feasible. For this reason we describe the relevant developments in ab initio molecular dynamics leading to this stage. Among them, parallel implementations, different basis set functions, density functionals, and van der Waals corrections are reported. The chemical features accessible through AIMD are discussed. These are IR, NMR, as well as EXAFS spectra, sampling methods like metadynamics and others, Wannier functions, dipole moments of molecules in condensed phase, and many other properties. Electrochemical reactions investigated by ab initio molecular dynamics methods in solution, on surfaces as well as complex interfaces, are also presented.
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Affiliation(s)
- Barbara Kirchner
- Wilhelm-Ostwald Institute of Physical and Theoretical Chemistry, University of Leipzig, Linnéstr. 2, 04103 Leipzig, Germany.
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30
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Hernández ER, Rodriguez-Prieto A, Bergara A, Alfè D. First-principles simulations of lithium melting: stability of the bcc phase close to melting. PHYSICAL REVIEW LETTERS 2010; 104:185701. [PMID: 20482189 DOI: 10.1103/physrevlett.104.185701] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 02/15/2010] [Indexed: 05/29/2023]
Abstract
We report large-scale first-principles simulations of melting of four different phases of Li at pressures ranging from 0 to 50 GPa. We find excellent agreement with existing experimental data at low pressures, and confirm that above 10 GPa the melting line develops a negative slope, in parallel to what occurs for Na at 30 GPa. Surprisingly, our results indicate that the melting temperature of the bcc phase is always higher than that of fcc Li, suggesting the intriguing possibility of the existence of a narrow field of bcc stability separating the fcc and liquid phases, as predicted by Alexander and McTague [Phys. Rev. Lett. 41, 702 (1978)].
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Affiliation(s)
- E R Hernández
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de Bellaterra, 08193 Barcelona, Spain.
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31
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Holmström E, Bock N, Peery TB, Lizárraga R, De Lorenzi-Venneri G, Chisolm ED, Wallace DC. Ab initio method for locating characteristic potential-energy minima of liquids. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:051111. [PMID: 20364951 DOI: 10.1103/physreve.80.051111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Indexed: 05/29/2023]
Abstract
It is possible in principle to probe the many-atom potential surface using density functional theory (DFT). This will allow us to apply DFT to the Hamiltonian formulation of atomic motion in monatomic liquids by Wallace [Phys. Rev. E 56, 4179 (1997)]. For a monatomic system, analysis of the potential surface is facilitated by the random and symmetric classification of potential-energy valleys. Since the random valleys are numerically dominant and uniform in their macroscopic potential properties, only a few quenches are necessary to establish these properties. Here we describe an efficient technique for doing this. Quenches are done from easily generated "stochastic" configurations, in which the nuclei are distributed uniformly within a constraint limiting the closeness of approach. For metallic Na with atomic pair potential interactions, it is shown that quenches from stochastic configurations and quenches from equilibrium liquid molecular dynamics configurations produce statistically identical distributions of the structural potential energy. Again for metallic Na, it is shown that DFT quenches from stochastic configurations provide the parameters which calibrate the Hamiltonian. A statistical mechanical analysis shows how the underlying potential properties can be extracted from the distributions found in quenches from stochastic configurations.
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Affiliation(s)
- E Holmström
- Instituto de Física, Universidad Austral de Chile, Valdivia, Chile.
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33
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Wallace DC, Chisolm ED, Bock N. Improved model for the transit entropy of monatomic liquids. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:051201. [PMID: 19518441 DOI: 10.1103/physreve.79.051201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Indexed: 05/27/2023]
Abstract
In the original formulation of vibration-transit (V-T) theory for monatomic liquid dynamics, the transit contribution to entropy was taken to be a universal constant, calibrated to the constant-volume entropy of melting. This model suffers two deficiencies: (a) it does not account for experimental entropy differences of +/-2% among elemental liquids and (b) it implies a value of zero for the transit contribution to internal energy. The purpose of this paper is to correct these deficiencies. To this end, the V-T equation for entropy is fitted to an overall accuracy of +/-0.1% to the available experimental high-temperature entropy data for elemental liquids. The theory contains two nuclear motion contributions: (a) the dominant vibrational contribution S_{vib}(T/theta_{0}) , where T is temperature and theta_{0} is the vibrational characteristic temperature, and (b) the transit contribution S_{tr}(T/theta_{tr}) , where theta_{tr} is a scaling temperature for each liquid. The appearance of a common functional form of S_{tr} for all the liquids studied is a property of the experimental data, when analyzed via the V-T formula. The resulting S_{tr} implies the correct transit contribution to internal energy. The theoretical entropy of melting is derived in a single formula applying to normal and anomalous melting alike. An ab initio calculation of theta_{0} , based on density-functional theory, is reported for liquid Na and Cu. Comparison of these calculations with the above analysis of experimental entropy data provides verification of V-T theory. In view of the present results, techniques currently being applied in ab initio simulations of liquid properties can be employed to advantage in the further testing and development of V-T theory.
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Affiliation(s)
- Duane C Wallace
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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34
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Branicio PS, Rino JP, Gan CK, Tsuzuki H. Interaction potential for indium phosphide: a molecular dynamics and first-principles study of the elastic constants, generalized stacking fault and surface energies. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:095002. [PMID: 21817375 DOI: 10.1088/0953-8984/21/9/095002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Indium phosphide is investigated using molecular dynamics (MD) simulations and density-functional theory calculations. MD simulations use a proposed effective interaction potential for InP fitted to a selected experimental dataset of properties. The potential consists of two- and three-body terms that represent atomic-size effects, charge-charge, charge-dipole and dipole-dipole interactions as well as covalent bond bending and stretching. Predictions are made for the elastic constants as a function of density and temperature, the generalized stacking fault energy and the low-index surface energies.
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Affiliation(s)
- Paulo Sergio Branicio
- Materials Theory and Simulation Laboratory, Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, 138632, Singapore
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35
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Alfè D, Gillan MJ. Ab initio statistical mechanics of surface adsorption and desorption. I. H2O on MgO (001) at low coverage. J Chem Phys 2007; 127:114709. [PMID: 17887872 DOI: 10.1063/1.2772258] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a general computational scheme based on molecular dynamics (MD) simulation for calculating the chemical potential of adsorbed molecules in thermal equilibrium on the surface of a material. The scheme is based on the calculation of the mean force in MD simulations in which the height of a chosen molecule above the surface is constrained and subsequent integration of the mean force to obtain the potential of mean force and hence the chemical potential. The scheme is valid at any coverage and temperature, so that in principle it allows the calculation of the chemical potential as a function of coverage and temperature. It avoids all statistical mechanical approximations, except for the use of classical statistical mechanics for the nuclei, and assumes nothing in advance about the adsorption sites. From the chemical potential, the absolute desorption rate of the molecules can be computed, provided that the equilibration rate on the surface is faster than the desorption rate. We apply the theory by ab initio MD simulation to the case of H2O on MgO (001) in the low-coverage limit, using the Perdew-Burke-Ernzerhof (PBE) form of exchange correlation. The calculations yield an ab initio value of the Polanyi-Wigner frequency prefactor, which is more than two orders of magnitude greater than the value of 10(13) s(-1) often assumed in the past. Provisional comparison with experiment suggests that the PBE adsorption energy may be too low, but the extension of the calculations to higher coverages is needed before firm conclusions can be drawn. The possibility of including quantum nuclear effects by using path-integral simulations is noted.
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Affiliation(s)
- D Alfè
- London Centre for Nanotechnology, University College London, Gordon Street, London WC1H 0AH, United Kingdom
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36
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Raty JY, Schwegler E, Bonev SA. Electronic and structural transitions in dense liquid sodium. Nature 2007; 449:448-51. [PMID: 17898764 DOI: 10.1038/nature06123] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Accepted: 07/19/2007] [Indexed: 11/09/2022]
Abstract
At ambient conditions, the light alkali metals are free-electron-like crystals with a highly symmetric structure. However, they were found recently to exhibit unexpected complexity under pressure. It was predicted from theory--and later confirmed by experiment--that lithium and sodium undergo a sequence of symmetry-breaking transitions, driven by a Peierls mechanism, at high pressures. Measurements of the sodium melting curve have subsequently revealed an unprecedented (and still unexplained) pressure-induced drop in melting temperature from 1,000 K at 30 GPa down to room temperature at 120 GPa. Here we report results from ab initio calculations that explain the unusual melting behaviour in dense sodium. We show that molten sodium undergoes a series of pressure-induced structural and electronic transitions, analogous to those observed in solid sodium but commencing at much lower pressure in the presence of liquid disorder. As pressure is increased, liquid sodium initially evolves by assuming a more compact local structure. However, a transition to a lower-coordinated liquid takes place at a pressure of around 65 GPa, accompanied by a threefold drop in electrical conductivity. This transition is driven by the opening of a pseudogap, at the Fermi level, in the electronic density of states--an effect that has not hitherto been observed in a liquid metal. The lower-coordinated liquid emerges at high temperatures and above the stability region of a close-packed free-electron-like metal. We predict that similar exotic behaviour is possible in other materials as well.
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37
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Yoshimoto Y. Extended multicanonical method combined with thermodynamically optimized potential: Application to the liquid-crystal transition of silicon. J Chem Phys 2006; 125:184103. [PMID: 17115734 DOI: 10.1063/1.2363987] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A novel method is proposed to study first-order phase transition in real materials. It is applied to the liquid-crystal transition of silicon successfully. It consists of two parts: a direct simulation of the transition by an extended multicanonical ensemble with an order parameter defined with structure factors that characterize the transition, and optimization of a model interatomic potential in terms of the ensemble from an accurate one. These provide a principle to project a first-principles approach on a model-based approach conserving thermodynamic properties of multiple phases.
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Affiliation(s)
- Yoshihide Yoshimoto
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa-shi, Chiba, 2778581, Japan.
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38
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Alfè D, Gillan MJ. Absolute rate of thermal desorption from first-principles simulation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2006; 18:L451-L457. [PMID: 21690892 DOI: 10.1088/0953-8984/18/37/l02] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present a technique for computing by first-principles simulation the absolute desorption rate γ of adsorbate molecules from a surface for any coverage and temperature. The technique is valid when the thermal equilibration rate on the surface is faster than γ, and is based on an exact expression for γ in terms of the difference of non-configurational chemical potentials of gas-phase and adsorbed molecules. This difference is expressed in terms of a potential of mean force, which is computed by constrained first-principles molecular dynamics. The technique is applied to D(2)O on the MgO(001) surface at low coverage, using the generalized gradient approximation (GGA) for exchange-correlation energy. Comparisons with experimental temperature programmed desorption data allow an assessment of the accuracy of the GGA for the adsorption of D(2)O on MgO(001).
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Affiliation(s)
- D Alfè
- Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK. Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK. London Centre for Nanotechnology, University College London, Gower Street, London WC1E 6BT, UK
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39
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Correa AA, Bonev SA, Galli G. Carbon under extreme conditions: phase boundaries and electronic properties from first-principles theory. Proc Natl Acad Sci U S A 2006; 103:1204-8. [PMID: 16432191 PMCID: PMC1345714 DOI: 10.1073/pnas.0510489103] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Indexed: 11/18/2022] Open
Abstract
At high pressure and temperature, the phase diagram of elemental carbon is poorly known. We present predictions of diamond and BC8 melting lines and their phase boundary in the solid phase, as obtained from first-principles calculations. Maxima are found in both melting lines, with a triple point located at approximately 850 GPa and approximately 7,400 K. Our results show that hot, compressed diamond is a semiconductor that undergoes metalization upon melting. In contrast, in the stability range of BC8, an insulator to metal transition is likely to occur in the solid phase. Close to the diamond/liquid and BC8/liquid boundaries, molten carbon is a low-coordinated metal retaining some covalent character in its bonding up to extreme pressures. Our results provide constraints on the carbon equation of state, which is of critical importance for devising models of Neptune, Uranus, and white dwarf stars, as well as of extrasolar carbon-rich planets.
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Affiliation(s)
- Alfredo A Correa
- Department of Physics, University of California, Berkeley, CA 94720, USA
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40
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Wang X, Scandolo S, Car R. Carbon phase diagram from ab initio molecular dynamics. PHYSICAL REVIEW LETTERS 2005; 95:185701. [PMID: 16383918 DOI: 10.1103/physrevlett.95.185701] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2005] [Indexed: 05/05/2023]
Abstract
We compute the free energy of solid and liquid diamond from first-principles electronic structure theory using efficient thermodynamic integration techniques. Our calculated melting curve is in excellent agreement with the experimental estimate of the graphite-diamond-liquid triple point and is consistent with shock wave experiments. We predict the phase diagram of diamond at pressures and temperatures that are difficult to access experimentally. We confirm early speculations on the presence of a reentrant point in the diamond melting line but find no evidence for a first order liquid-liquid phase transition near the reentrant point.
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Affiliation(s)
- Xiaofei Wang
- Department of Chemistry and Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, USA
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41
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Alfè D. Melting curve of MgO from first-principles simulations. PHYSICAL REVIEW LETTERS 2005; 94:235701. [PMID: 16090481 DOI: 10.1103/physrevlett.94.235701] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2005] [Indexed: 05/03/2023]
Abstract
First-principles calculations based on density functional theory, both with the local density approximation (LDA) and with generalized gradient corrections (GGA), have been used to simulate solid and liquid MgO in direct coexistence in the range of pressure 0 < or = p < or = 135 GPa. The calculated LDA zero pressure melting temperature is T(LDA)m = 3110 +/- 50 K, in good agreement with the experimental data. The GGA zero pressure melting temperature T(GGA)m = 2575 +/- 100 K is significantly lower than the LDA one, but the difference between the GGA and the LDA is greatly reduced at high pressure. The LDA zero pressure melting slope is dT/dp approximately 100 K/GPa, which is more than 3 times higher than the currently available experimental one from Zerr and Boehler [Nature (London) 371, 506 (1994)]. At the core mantle boundary pressure of 135 GPa MgO melts at Tm = 8140 +/- 150 K.
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Affiliation(s)
- Dario Alfè
- Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom
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42
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Kaczmarski M, Bedoya-Martínez ON, Hernández ER. Phase diagram of silicon from atomistic simulations. PHYSICAL REVIEW LETTERS 2005; 94:095701. [PMID: 15783976 DOI: 10.1103/physrevlett.94.095701] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Indexed: 05/24/2023]
Abstract
In this Letter we present a calculation of the temperature-pressure phase diagram of Si in a range of pressures covering from -5 to 20 GPa and temperatures up to the melting point. The phase boundaries and triple points between the diamond, liquid, beta-Sn, and Si34 clathrate phases are reported. We have employed efficient simulation techniques to calculate free energies and to numerically integrate the Clausius-Clapeyron equation, combined with a tight-binding model capable of an accuracy comparable to that of first-principles methods. The resulting phase diagram agrees well with the available experimental data.
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Affiliation(s)
- M Kaczmarski
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus de Bellaterra, 08193 Barcelona, Spain
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43
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Miranda CR, Antonelli A. Transitions between disordered phases in supercooled liquid silicon. J Chem Phys 2004; 120:11672-7. [PMID: 15268202 DOI: 10.1063/1.1755653] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have investigated the transitions between disordered phases in supercooled liquid silicon using computer simulations. The thermodynamic properties were directly obtained from the free energy, which was computed using the recently proposed reversible scaling method. The calculated free energies of the crystalline and liquid phases of silicon at zero pressure, obtained using the environment dependent interatomic potential, are in excellent agreement with the available experimental data. The results show that, at zero pressure, a weak first-order liquid-liquid transition occurs at 1135 K and a continuous liquid-amorphous transition takes place at 843 K. These results are consistent with the existence of a second critical point for the liquid-liquid transition at a negative pressure.
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Affiliation(s)
- Caetano R Miranda
- Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas, CP 6165, CEP 13083-970, Campinas, SP, Brazil.
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44
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Vocadlo L, Alfè D, Price GD, Gillan MJ. Ab initiomelting curve of copper by the phase coexistence approach. J Chem Phys 2004; 120:2872-8. [PMID: 15268434 DOI: 10.1063/1.1640344] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Ab initio calculations of the melting properties of copper in the pressure range 0-100 GPa are reported. The ab initio total energies and ionic forces of systems representing solid and liquid copper are calculated using the projector augmented wave implementation of density functional theory with the generalized gradient approximation for exchange-correlation energy. An initial approximation to the melting curve is obtained using an empirical reference system based on the embedded-atom model, points on the curve being determined by simulations in which solid and liquid coexist. The approximate melting curve so obtained is corrected using calculated free energy differences between the reference and ab initio system. It is shown that for system-size errors to be rendered negligible in this scheme, careful tuning of the reference system to reproduce ab initio energies is essential. The final melting curve is in satisfactory agreement with extrapolated experimental data available up to 20 GPa, and supports the validity of previous calculations of the melting curve up to 100 GPa.
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Affiliation(s)
- L Vocadlo
- Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, United Kingdom.
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45
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Ogitsu T, Schwegler E, Gygi F, Galli G. Melting of lithium hydride under pressure. PHYSICAL REVIEW LETTERS 2003; 91:175502. [PMID: 14611356 DOI: 10.1103/physrevlett.91.175502] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2003] [Indexed: 05/24/2023]
Abstract
We have computed the melting line of lithium hydride up to 200 GPa using the two-phase simulation technique coupled with first-principles molecular dynamics. Our predicted melting temperature at high pressures varies slowly with compression, ranging from 2000 to 2450 K at 50-200 GPa pressures. The compressed fluid close to the melting line retains the ionic character of the low pressure molten state, while at higher temperatures dynamical hydrogen clustering processes are observed, which are accompanied by changes in the electronic structure.
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Affiliation(s)
- Tadashi Ogitsu
- Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94550, USA
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46
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Mantz YA, Geiger FM, Molina LT, Molina MJ, Trout BL. A Theoretical Study of the Interaction of HCl with Crystalline NAT. J Phys Chem A 2002. [DOI: 10.1021/jp0144754] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Yves A. Mantz
- Department of Earth, Atmospheric, and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307
| | - Franz M. Geiger
- Department of Earth, Atmospheric, and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307
| | - Luisa T. Molina
- Department of Earth, Atmospheric, and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307
| | - Mario J. Molina
- Department of Earth, Atmospheric, and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307
| | - Bernhardt L. Trout
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307
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Alfè D, Gillan MJ, Price GD. Ab initio chemical potentials of solid and liquid solutions and the chemistry of the Earth’s core. J Chem Phys 2002. [DOI: 10.1063/1.1464121] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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48
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Alfè D, Gillan MJ, Price GD. Complementary approaches to the ab initio calculation of melting properties. J Chem Phys 2002. [DOI: 10.1063/1.1460865] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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49
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Tangney P, Scandolo S. How well do Car–Parrinello simulations reproduce the Born–Oppenheimer surface? Theory and examples. J Chem Phys 2002. [DOI: 10.1063/1.1423331] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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50
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Oganov AR, Brodholt JP, Price GD. The elastic constants of MgSiO3 perovskite at pressures and temperatures of the Earth's mantle. Nature 2001; 411:934-7. [PMID: 11418854 DOI: 10.1038/35082048] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The temperature anomalies in the Earth's mantle associated with thermal convection can be inferred from seismic tomography, provided that the elastic properties of mantle minerals are known as a function of temperature at mantle pressures. At present, however, such information is difficult to obtain directly through laboratory experiments. We have therefore taken advantage of recent advances in computer technology, and have performed finite-temperature ab initio molecular dynamics simulations of the elastic properties of MgSiO3 perovskite, the major mineral of the lower mantle, at relevant thermodynamic conditions. When combined with the results from tomographic images of the mantle, our results indicate that the lower mantle is either significantly anelastic or compositionally heterogeneous on large scales. We found the temperature contrast between the coldest and hottest regions of the mantle, at a given depth, to be about 800 K at 1,000 km, 1,500 K at 2,000 km, and possibly over 2,000 K at the core-mantle boundary.
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Affiliation(s)
- A R Oganov
- Department of Geological Sciences, University College London, UK.
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