A first principle study of pristine and BN-doped graphyne family

DFT investigation of geometrical, vibrational, elastic, electronic, optical, and thermoelectric properties of aluminum pnictogens compounds

The aim of this study is to investigate the geometrical, vibrational, elastic, electronic, optical, and thermoelectric characteristics of aluminum pnictides in monolayer square lattice and bilayer hexagonal phases (s- and h-AlX; X = N, P, As) using first principles. The s- and h-AlX materials are mechanically, energetically, and dynamically stable, through phonon dispersion and elastic properties investigations. It was observed that s-AlX materials exhibited both direct and indirect bandgaps, whereas h-AlX materials exhibited indirect bandgap behavior. The energy bandgap values for s- and h-AlX materials measured between 0.79 eV and 3.49 eV for the PBE functional, and between 1.49 eV and 4.74 eV for the HSE06 functional. The effective mass, mobility and relaxation time of electron carriers as well as hole carriers from the band structure of s- and h-AlX are examined to gain a better perception into these materials. The AlP monolayer square lattice phase has the highest mobility and relaxation time of 266129.60 cm2V-1s-1 and 740369.83 fs among entire s- and h-AlX materials. The optical characteristics of s- and h-AlX materials are examined in the existence of field polarizations. The thermoelectric properties of the AlX materials are assessed for temperature dependent. Our investigated results expose that AlP/AlP and AlAs/AlAs are the proficient thermoelectric materials at room temperature in the considered sequence. The present investigation shows that the s- and h-AlX materials are mostly active in the UV region of electromagnetic spectrum, and may find applications in UV-photodetectors and UV-protectant materials.

Transferable machine learning interatomic potential for carbon hydrogen systems

In this study, we developed a machine learning interatomic potential based on artificial neural networks (ANN) to model carbon-hydrogen (C-H) systems. The ANN potential was trained on a dataset of C-H clusters obtained through density functional theory (DFT) calculations. Through comprehensive evaluations against DFT results, including predictions of geometries and formation energies across 0D-3D systems comprising C and C-H, as well as modeling various chemical processes, the ANN potential demonstrated exceptional accuracy and transferability. Its capability to accurately predict lattice dynamics, crucial for stability assessment in crystal structure prediction, was also verified through phonon dispersion analysis. Notably, its accuracy and computational efficiency in calculating force constants facilitated the exploration of complex energy landscapes, leading to the discovery of a novel C polymorph. These results underscore the robustness and versatility of the ANN potential, highlighting its efficacy in advancing computational materials science by conducting precise atomistic simulations on a wide range of C-H materials.

Developments in Synthesis and Potential Electronic and Magnetic Applications of Pristine and Doped Graphynes

Doping and its consequences on the electronic features, optoelectronic features, and magnetism of graphynes (GYs) are reviewed in this work. First, synthetic strategies that consider numerous chemically and dimensionally different structures are discussed. Simultaneous or subsequent doping with heteroatoms, controlling dimensions, applying strain, and applying external electric fields can serve as effective ways to modulate the band structure of these new sp2/sp allotropes of carbon. The fundamental band gap is crucially dependent on morphology, with low dimensional GYs displaying a broader band gap than their bulk counterparts. Accurately chosen precursors and synthesis conditions ensure complete control of the morphological, electronic, and physicochemical properties of resulting GY sheets as well as the distribution of dopants deposited on GY surfaces. The uniform and quantitative inclusion of non-metallic (B, Cl, N, O, or P) and metallic (Fe, Co, or Ni) elements into graphyne derivatives were theoretically and experimentally studied, which improved their electronic and magnetic properties as row systems or in heterojunction. The effect of heteroatoms associated with metallic impurities on the magnetic properties of GYs was investigated. Finally, the flexibility of doped GYs' electronic and magnetic features recommends them for new electronic and optoelectronic applications.

Graphyne-3: a highly efficient candidate for separation of small gas molecules from gaseous mixtures

Two-dimensional nanosheets, such as the general family of graphenes have attracted considerable attention over the past decade, due to their excellent thermal, mechanical, and electrical properties. We report on the result of a study of separation of gaseous mixtures by a model graphyne-3 membrane, using extensive molecular dynamics simulations and density functional theory. Four binary and one ternary mixtures of H[Formula: see text], CO[Formula: see text], CH[Formula: see text] and C[Formula: see text]H[Formula: see text] were studied. The results indicate the excellence of graphyne-3 for separation of small gas molecules from the mixtures. In particular, the H[Formula: see text] permeance through the membrane is on the order of [Formula: see text] gas permeation unit, by far much larger than those in other membranes, and in particular in graphene. To gain deeper insights into the phenomenon, we also computed the density profiles and the residence times of the gases near the graphyne-3 surface, as well as their interaction energies with the membrane. The results indicate clearly the tendency of H[Formula: see text] to pass through the membrane at high rates, leaving behind C[Formula: see text]H[Formula: see text] and larger molecules on the surface. In addition, the possibility of chemisorption is clearly ruled out. These results, together with the very good mechanical properties of graphyne-3, confirm that it is an excellent candidate for separating small gas molecules from gaseous mixtures, hence opening the way for its industrial use.

Thermoelectric Properties of Pristine Graphyne and the BN-Doped Graphyne Family

In this paper, we have investigated the thermoelectric properties of BN-doped graphynes and compared them with respect to their pristine counterpart using first-principles calculations. The effect of temperature on the thermoelectric properties has also been explored. Pristine γ-graphyne is an intrinsic band gap semiconductor and the band gap significantly increases due to the incorporation of boron and nitrogen atoms into the system, which simultaneously results in high electrical conductivity, a large Seebeck coefficient, and low thermal conductivity. The Seebeck coefficient for all these systems is significantly higher than that of conventional thermoelectric materials, suggesting their potential in thermoelectric applications. Among all the considered systems, the "graphyne-like BN sheet" has the highest electrical conductance and lowest thermal conductance, ensuring its superiority in thermoelectric properties over the other studied systems. We find that a maximum full ZT of ∼6 at room temperature is accessible in the "graphyne-like BN sheet".

The Accelerating World of Graphdiynes

Graphdiyne (GDY), a 2D allotrope of graphene, is first synthesized in 2010 and has attracted attention as a new low-dimensional carbon material. This work surveys the literature on GDYs. The history of GDYs is summarized, including their relationship with 2D graphyne carbons and yearly publication trends. GDY is a molecule-based nanosheet woven from a molecular monomer, hexaethynylbenzene; thus, it is synthesized by bottom-up approaches, which allow rich variation via monomer design. The GDY family and the synthetic procedures are also described. Highly developed π-conjugated electronic structures are common important features in GDY and graphene; however, the coexistence of sp and sp² carbons differentiates GDY from graphene. This difference gives rise to unique physical properties, such as high conductivity and large carrier mobility. Next, the theoretical and experimental studies of these properties are described in detail. A wide variety of applications are proposed for GDYs, including electrocatalysts and energy devices, which exploit the carbon-rich nature, porous framework, and expanded π-electron system of these compounds. Finally, potential uses are discussed.

Acetylenic linkage dependent electronic and optical behaviour of morphologically distinct ‘-ynes’

We have critically examined the key role of acetylenic linkages (–CC–) in determining the opto-electronic responses of the dynamically stable tetragonal (T) ‘-ynes’ with the help of density functional theory.

The spin filtering effect and negative differential behavior of the graphene-pentalene-graphene molecular junction: a theoretical analysis

Density functional theory (DFT) combined with nonequilibrium Green's function (NEGF) formalism are used to investigate the effects of substitutional doping by nitrogen and sulfur on transport properties of AGNR-pentalene-AGNR nanojunction. A considerable spin filtering capability in a wide bias range is observed for all systems, which may have potential application in spintronics devices. Moreover, all model devices exhibit a negative differential effect with considerable peak-to-valley ratio. Thus, our findings provide a way to produce multifunctional spintronic devices based on nitrogen and sulfur doped pentalene-AGNR nanojunctions. The underlying mechanism for this interesting behavior was exposed by analyzing the transmission spectrum as well as the electrostatic potential distribution. In addition, a system doped with an odd number of dopant shows a rectifying efficiency comparable to other systems. The above findings strongly imply that such a multifunctional molecular device would be a useful candidate for molecular electronics. Graphical abstract The graphene-pentalene-graphene molecular junction.

Molecular dynamics investigation of the mechanical behavior of multi-layered graphyne and its family under tensile loading

This paper aims to study the mechanical properties of the multi-layered graphyne and other members of the graphyne family under the uniaxial tensile loading. For this purpose, molecular dynamics simulations are used. The effects of the size and number of layers on the fracture and elastic properties are studied. It is shown that Young's modulus of the zigzag multi-layered graphyne is slightly larger than armchair one. Comparing the stress-strain curves of the multi-layered graphynes with different number of layers, it is observed that the fracture stress and strain of the nanosheets are inversely related to the number of layers. Investigating the influence of the number of acetylene linkage in the structure of the graphyne-n family on their mechanical properties, it is shown increasing the number of triple bonds leads to weakening the fracture stress and Young's modulus of the nanosheet.

Electronic and optical properties of pristine and boron–nitrogen doped graphyne nanotubes

The band gaps and optical responses of graphyne nanotubes can be engineered through the selection of the BN doping site and the chirality.

Flexible band gap tuning of hexagonal boron nitride sheets interconnected by acetylenic bonds

Periodically embedded acetylenic chains in BN sheets provide flexible band-gap engineering with opposite overall tendencies in oscillating manner.