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Krstic PS, Dwivedi S, Ostrowski ET, Abe S, Maan A, van Duin ACT, Koel BE. Hydrogen irradiation-driven computational surface chemistry of lithium oxide and hydroxide. J Chem Phys 2023; 159:244703. [PMID: 38153149 DOI: 10.1063/5.0177460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 12/04/2023] [Indexed: 12/29/2023] Open
Abstract
We have investigated, using molecular dynamics, the surface chemistry of hydrogen incident on the amorphous and crystalline lithium oxide and lithium hydroxide surfaces upon being slowed down by a collision cascade and retained in the amorphous surface of either Li2O or LiOH. We looked for the bonding of H to the resident structures in the surface to understand a possible chain of chemical reactions that can lead to surface transformation upon H atom impact. Our findings, using Density-Functional Theory (DFT) trained ReaxFF force field/electronegativity equalization method potentials, stress the importance of inclusion of polarization in the dynamics of a Li-O-H system, which is also illustrated by DFT energy minimization and quantum-classical molecular dynamics using tight binding DFT. The resulting polar-covalent chemistry of the studied systems is complex and very sensitive to the instantaneous positions of all atoms as well as the ratio of concentrations of various resident atoms in the surface.
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Affiliation(s)
- P S Krstic
- TheoretiK, Port Jefferson Station, New York 11776, USA
- Stony Brook University, Stony Brook, New York 11749, USA
| | - S Dwivedi
- Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - E T Ostrowski
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - S Abe
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - A Maan
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - A C T van Duin
- Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - B E Koel
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
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Maan A, Kaita R, Ostrowski ET, Majeski R, Boyle DP, Donovan DC, Ellis RA, Koel BE, Biewer TM. A simple vacuum suitcase for enabling plasma facing component characterization in fusion devices. Rev Sci Instrum 2020; 91:026104. [PMID: 32113407 DOI: 10.1063/1.5119166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 01/18/2020] [Indexed: 06/10/2023]
Abstract
We have demonstrated a vacuum suitcase to transport samples in vacuo to a surface analysis station for characterization of tokamak plasma facing components (PFCs). This technique enables surface analysis at powerful, dedicated stations that are not encumbered by design constraints imposed on them by a tokamak. The vacuum suitcase is an alternative solution to characterizing PFCs using diagnostics that are designed and built around a tokamak. The vacuum suitcase, called the Sample Exposure Probe (SEP), features mobile ultra-high vacuum pumping. Active pumping under high vacuum enables sample transfer between the Lithium Tokamak eXperiment-β (LTX-β) and a high resolution X-ray Photoelectron Spectroscopy (XPS) system that is situated close by. A thermocouple inserted in the back of the sample head measures heat flux from the plasma during exposure, and together with a button heater, allows the sample to match the LTX-β PFCs in high temperature operations. As vacuum conditions are better during transfer and analysis than in the tokamak, less contamination is introduced to the samples. XPS scans on a dedicated analysis station enable peak identification due to higher resolution and signal to noise ratio. A similar probe could be implemented for other fusion devices. The SEP is the first vacuum suitcase implementation for fusion applications that incorporates active pumping.
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Affiliation(s)
- A Maan
- Nuclear Engineering, University of Tennessee, Knoxville, Tennessee 37796, USA
| | - R Kaita
- Nuclear Engineering, University of Tennessee, Knoxville, Tennessee 37796, USA
| | - E T Ostrowski
- Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - R Majeski
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - D P Boyle
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - D C Donovan
- Nuclear Engineering, University of Tennessee, Knoxville, Tennessee 37796, USA
| | - R A Ellis
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA
| | - B E Koel
- Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - T M Biewer
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
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Bedoya F, Allain JP, Kaita R, Skinner CH, Buzi L, Koel BE. Unraveling wall conditioning effects on plasma facing components in NSTX-U with the Materials Analysis Particle Probe (MAPP). Rev Sci Instrum 2016; 87:11D403. [PMID: 27910555 DOI: 10.1063/1.4955276] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A novel Plasma Facing Components (PFCs) diagnostic, the Materials Analysis Particle Probe (MAPP), has been recently commissioned in the National Spherical Torus Experiment Upgrade (NSTX-U). MAPP is currently monitoring the chemical evolution of the PFCs in the NSTX-U lower divertor at 107 cm from the tokamak axis on a day-to-day basis. In this work, we summarize the methodology that was adopted to obtain qualitative and quantitative descriptions of the samples chemistry. Using this methodology, we were able to describe all the features in all our spectra to within a standard deviation of ±0.22 eV in position and ±248 s-1 eV in area. Additionally, we provide an example of this methodology with data of boronized ATJ graphite exposed to NSTX-U plasmas.
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Affiliation(s)
- F Bedoya
- Department of Nuclear, Plasma and Radiological Engineering, University of Illinois, Urbana, Illinois 61801, USA
| | - J P Allain
- Department of Nuclear, Plasma and Radiological Engineering, University of Illinois, Urbana, Illinois 61801, USA
| | - R Kaita
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - C H Skinner
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - L Buzi
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540, USA
| | - B E Koel
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540, USA
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Yang XF, Xu W, Li M, Koel BE, Chen JG. A new class of electrocatalysts of supporting Pt on an Engel-Brewer alloy substrate: a demonstration for oxidation of ethylene glycol. Chem Commun (Camb) 2014; 50:12981-4. [PMID: 25219415 DOI: 10.1039/c4cc04006f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel electrocatalytic surface consisting of a Pt monolayer (ML) on an Hf-Ir alloy substrate demonstrated significantly higher activity (six times) and higher selectivity to CO2 formation than bulk Pt in oxidizing ethylene glycol. This enhanced performance could be associated with the high reducibility of Hf oxide and altered electronic property of the Pt ML.
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Affiliation(s)
- X F Yang
- Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, USA
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Matsumoto T, Ho CS, Batzill M, Roszell JP, Koel BE. Ge overlayer and surface alloy structures on Pt(100) studied using alkali ion scattering spectroscopy, x-ray photoelectron spectroscopy and x-ray photoelectron diffraction. J Phys Condens Matter 2014; 26:135002. [PMID: 24614055 DOI: 10.1088/0953-8984/26/13/135002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We have investigated surface structures formed by deposition of Ge on a Pt(100) substrate by using a multi-technique approach utilizing alkali ion scattering spectroscopy (ALISS), x-ray photoelectron spectroscopy (XPS), and x-ray photoelectron diffraction (XPD). ALISS was used to distinguish Ge overlayers from incorporated alloy layers for the surface structures reported, and to supply structural information about the surface alloy or 'layer compound' formed by the deposition of 1.5-ML Ge. A Ge adlayer forms following the deposition of 0.2-ML Ge on Pt(100) and annealing at 600 K. ALISS revealed that Ge adatoms in these overlayers had 1D (incomplete c(2 × 2)) Ge-Ge ordering along [010] and equivalent directions, even though this was not directly apparent in observations using LEED and STM. A c(2 × 2)-Ge overlayer was produced after 0.5 ML-Ge deposition on Pt(100) and annealing at 600 K. Deposition of 1.5-ML Ge on Pt(100) and annealing at 600 K caused extensive Ge interdiffusion into the third (subsurface) layer, while the first and second layers remained as a c(2 × 2) Ge overlayer and (1 × 1) Pt layer, respectively. We propose that the Pt(100) substrate thus is 'capped' by an alloy film with the structure of a body-centered tetragonal Pt2Ge layer compound, which is terminated by a pure-Ge layer that is indistinguishable from a c(2 × 2)-Ge adlayer. This explains the apparently 'strange' result that even though extensive Ge interdiffusion was occurring deeply into the Pt bulk during annealing at 900 and 1200 K, a Ge overlayer remained on the surface. XPS spectra showed a +0.5 eV binding energy shift of the Ge 3d core level and a small (0-0.1 eV) positive shift of the Pt 5d core level compared to Ge(100) and Pt(100) surfaces for the c(2 × 2)-Ge overlayer. There was no effect on these binding energies upon formation of the Pt2Ge layer compound at the surface, and this indicates similar Ge-Pt interactions in the two cases. Compared to other overlayers of Group-IV atoms on metal surfaces, the Ge overlayer on Pt(100) was extraordinarily stable.
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Wang KS, Resch R, Koel BE, Shuler PJ, Tang Y, Chen H, Yen TF. Study of the Dissolution of the Barium Sulfate (001) Surface with Hydrochloric Acid by Atomic Force Microscopy. J Colloid Interface Sci 1999; 219:212-215. [PMID: 10527591 DOI: 10.1006/jcis.1999.6473] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Noncontact atomic force microscopy (NC-AFM) has been used to investigate the morphological changes of a freshly cleaved (001) surface of barium sulfate (barite) etched with an aqueous solution of 0.1 M HCl at room temperature. Shallow triangular etch pits with a height of 3.6 Å were developed in atomically flat (001) terraces. The etching of the surface was found to proceed in a layer-by-layer dissolution process. Because the crystal structure of barite exhibits a two-fold screw axis parallel to the c axis, "alternating" etch pits were formed, with any two consecutive etch pits pointing opposite to each other. These etch pits became deeper and more elongated along the b axis with time. Copyright 1999 Academic Press.
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Affiliation(s)
- KS Wang
- Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, California, 90089
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Sellidj A, Koel BE. Electronic and CO chemisorption properties of ultrathin Pd films vapor deposited on Au(111). Phys Rev B Condens Matter 1994; 49:8367-8376. [PMID: 10009605 DOI: 10.1103/physrevb.49.8367] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Li YD, Jiang LQ, Koel BE. Surface alloy formation and the structure of c(2 x 2)-Sn/Ni(100) determined by low-energy alkali-ion scattering. Phys Rev B Condens Matter 1994; 49:2813-2820. [PMID: 10011115 DOI: 10.1103/physrevb.49.2813] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Jiang LQ, Li YD, Koel BE. Trajectory-dependent neutralization of low energy Li+ scattered from alkali adsorbates on Ni(111). Phys Rev Lett 1993; 70:2649-2652. [PMID: 10053616 DOI: 10.1103/physrevlett.70.2649] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Koel BE, Sellidj A, Paffett MT. Ultrathin films of Pd on Au(111): Evidence for surface alloy formation. Phys Rev B Condens Matter 1992; 46:7846-7856. [PMID: 10002526 DOI: 10.1103/physrevb.46.7846] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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