The elastic properties and lattice dynamics of Ti$_2$AlC, Ti$_2$AlN, Ti$_2$GaC, Ti$_2$GaN, Ti$_2$PbC, Ti$_2$CdC and Ti$_2$SnC have been investigated using the density functional theory within the generalized gradient approximations as expressed in Quantum Espresso and VASP codes. The obtained lattice parameters are in agreement with the previous theoretical research and available experimental data. The elastic properties of the MAX phases under study have been calculated. The values of elastic anisotropy, Young's modulus, Poisson ratio and shear modulus reveal that the compounds are stable and ductile and that Ti$_2$PbC and Ti$_2$CdC are more stable than the other considered compounds. Thus, the seven compounds may be useful for industrial applications. The calculated phonon spectra confirm that the studied MAX phases are dynamically stable because of the absence of imaginary phonon modes. The temperature dependent lattice thermal conductivity of MAX phases have been determined using the Debye theory as outlined by Slack. The obtained $κ_{ph}$ for Ti$_2$AlC at 1300 K agree with experimental findings within 9$\%$. The estimated minimum thermal conductivities ($κ_{min}$) of the MAX phases obtained by using empirical formula suggested by Clarke show that Ti$_2$PbC possesses the lowest minimum thermal conductivity.
With the help of first principles calculation method based on the density functional theory we have investigated the structural, elastic, mechanical properties and Debye temperature of Fe2ScM (M = P and As) compounds under pressure up to 60 GPa. The optical properties have been investigated under zero pressure. Our calculated optimized structural parameters of both the compounds are in good agreement with the other theoretical results. The calculated elastic constants show that Fe2ScM (M = P and As) compounds are mechanically stable up to 60 GPa.
Materials under complex loading develop large strains and often transition via an elastic instability, as observed in both simple and complex systems. Here, we present Si I under large strain in terms of Lagrangian strain by an $5^{th}$-order elastic potential found by minimizing error relative to density functional theory (DFT) results. The Cauchy stress-Lagrangian strain curves for arbitrary complex loadings are in excellent correspondence with DFT results, including elastic instability driving Si I$\rightarrow$II phase transformation (PT) and the shear instabilities. PT conditions for Si I$…
Studies aimed at designing new allotropic forms of carbon have received much attention. Recently, a new 2D graphene-like allotrope named Pentahexoctite was theoretically proposed. Pentahexoctite has a metallic signature, and its structure consists of continuous 5-6-8 rings of carbon atoms with sp2 hybridization. Here, we carried out fully-atomistic computational simulations, combining reactive (ReaxFF) molecular dynamics (MD) and density functional theory (DFT) methods, to study the elastic properties and fracture patterns of Pentahexoctite monolayer. Results revealed a Young's Modulus of 0.74…
Theoretical investigation of structural, elastic, electronic and bonding properties of A-15 Nb-based intermetallic compounds Nb3B (B = Pt, Os) have been performed using first principles calculations based on the density functional theory (DFT). Optimized cell parameters are found to be in good agreement with available experimental and theoretical results. The elastic constants at zero pressure and temperature are calculated and the anisotropic behaviors of the compounds are studied. Both the compounds are mechanically stable and ductile in nature. Other elastic properties such as Pugh's ratio,…
Using density functional theory (DFT) and density functional perturbation theory (DFPT), we investigate the stability and response functions of CsH$_2$PO$_4$, a ferroelectric material at low temperature. This material cannot be described properly by the usual (semi-)local approximations within DFT. The long-range e$^-$-e$^-$ correlation needs to be properly taken into account, using, for instance, Grimme's DFT-D methods, as investigated in this work. We find that DFT-D3(BJ) performs the best for the members of the dihydrogenated alkali phosphate family (KH$_2$PO$_4$, RbH$_2$PO$_4$, CsH$_2$PO$_…
In the present paper, hcp Re was investigated in terms of its structural, elastic, mechanical and thermodynamic properties using density-functional theory (DFT). The local density approximation was employed for the exchange-correlation potential together with spin-orbit coupling. The computed lattice constant was found to be in agreement with the available experimental and theoretical results. The elastic constants were also calculated and used to determine mechanical properties like Young's modulus (Y), the shear modulus (G), Poisson's ratio (n) and Vicker's hardness. From thermodynamic inves…
PbTaSe2 is a non-centrosymmetric topological semimetal. In this work we have explored the structural, elastic, mechanical, bonding, electronic, acoustic, thermal, and optical properties of PbTaSe2. The electronic bond structure calculations confirm semi-metallic character. Fermi surface topology shows both electron and hole sheets. The single crystal elastic constants reveal that PbTaSe2 is elastically stable. The compound is soft, brittle, and highly machinable at the same time. It also possesses very high level of dry lubricity. Various anisotropy indicators suggest that PbTaSe2 is elastical…
By applying density functional theory (DFT) approximations, we present a first-principles investigation of elastic properties for the experimentally verified phases of a metallic perovskite LaNiO$_{3}$. In order to improve the accuracy of calculations, at first we select the most appropriate DFT approaches according to their performance in reproducing the low-temperature crystalline structure and the electronic density of states observed for the bulk LaNiO$_{3}$. Then, we continue with the single-crystal elastic constants and mechanical stability for the most common rhombohedral as well as hig…
The physical characteristics of the novel chalcogenide MAX phase Hf2SeC have been investigated using the DFT method. The obtained lattice constant and elastic constants (Cij) are compared with previous results to check the consistency of our setting parameters during calculations Moreover, the elastic properties such as elastic constants, moduli, anisotropy, and hardness are also compared with preexisting MAX phases of its kind. The checking of mechanical stability has been done based on Cij in accordance with the previously stated stability criteria. The reason for the higher hardness of Hf2S…
Half-metallicity, low magnetic damping and high curie temperature (TC) are crucial for application in spintronics and full Heusler alloys in this regard exhibit remarkable properties. Herein, we have considered Co2FeAl (CFA) and Fe2CoAl (FCA) as a representative of direct and indirect full Heusler compounds which crystallises in L21 and C1b phases, respectively. The theory of L21 type Heusler alloys has been well established, however the fundamental understanding of Fe2CoAl is still under developed. In this paper, we have employed density functional theory (DFT) to study the electronic, elasti…
Si$_{y}$Ge$_{1-x-y}$(C,Sn,Pb)$_{x}$ alloys have attracted significant attention as a route to achieve a direct-gap group-IV semiconductor. Using density functional theory (DFT) - employing local density approximation and hybrid Heyd-Scuzeria-Ernzerhof exchange-correlation functionals - we compute the lattice parameters, relaxed and inner elastic constants, and internal strain (Kleinman) parameters for elemental (diamond) group-IV materials and zinc blende IV-IV compounds. Our DFT calculations support a little-known experimental re-evaluation of the $α$-Sn elastic constants, and contradict a re…
Recently, Bafekry et al. [Appl. Phys. Lett. 119, 142102 (2021)] reported their density functional theory (DFT) results on the elastic constants of a novel C6N7 monolayer. They predicted a very soft elastic modulus of 36.29 GPa for the C6N7 monolayer, which is remarkably low for carbon-nitride 2D lattices. Using DFT calculations, we predict a remarkably higher elastic modulus of 267 GPa for this monolayer. The maximum tensile strength is also predicted to be 20.5 GPa, revealing the outstanding mechanical properties of the C6N7 monolayer.
Structural, elastic, electronic and optical properties of laves phase intermetallic compounds CaRh2 and LaRh2 prototype with MgCu2 are investigated by using the first principle calculations. These calculations stand on density functional theory (DFT) from CASTEP code. The calculated lattice parameters are consistent with the experimental values. The significant elastic properties, like as bulk modulus, shear modulus, Youngs modulus and the Poissons ratio are determined by applying the Voigt Reuss Hill (VRH) approximation. The analysis of Pughs ratio shows the ductile nature of both the phases.…
We present a first-principles investigation of structural and elastic properties of experimentally observed phases of bulk SrRuO$_3$ - namely orthorhombic, tetragonal, and cubic - by applying density functional theory (DFT) approximations. At first, we focus our attention on the accuracy of calculated lattice constants in order to find out DFT approaches that best represent the crystalline structure of SrRuO$_3$, since many important physical quantities crucially depend on change in volume. Next, we evaluate single-crystal elastic constants, mechanical stability, and macroscopic elastic parame…
Structural, elastic, electronic, bonding, thermo-mechanical and optical properties of predicted NbAlB MAB phase in comparison to MoAlB: DFT based ab-initio insights
Quantum-mechanical (QM) simulations, thanks to their predictive power, can provide significant insights into the nature and dynamics of defects such as vacancies, dislocations and grain boundaries. These considerations are essential in the context of the development of reliable, inexpensive and environmentally friendly alloys. However, despite significant progress in computer performance, QM simulations of defects are still extremely time-consuming with ab-initio/non-parametric methods. The two-centre Slater-Koster (SK) tight-binding (TB) models can achieve significant computational efficiency…
Transformer-based prediction of two-dimensional material electronic properties under elastic strain engineering
School of Materials Science and Engineering, Beijing Institute of Technology（北京理工大学材料学院）；School of Chemistry and Chemical Engineering, Beijing Institute of Technology（北京理工大学化学与化学工程学院）
Density functional theory (DFT) based first-principles investigations of structural, elastic, electronic band structure, and optical properties of superconducting ternary phosphides (BaM2P2; M = Ni, Rh) have been carried out in this study. This is the first detailed pressure dependent study of these properties for the titled compounds. The calculated ambient condition properties are compared with existing experimental and theoretical results, where available. The pressure dependent variations of the electronic density of states at the Fermi level, N(EF), and the Debye temperature, thetaD, have…
Closely packed quasi-hexagonal and quasi-tetragonal crystalline phase of C$_{60}$ molecules (named qHPC$_{60}$) was recently synthesized. Here, we used DFT simulations to investigate the electronic, optical, and mechanical properties of qHPC$_{60}$ monolayers. qHPC$_{60}$ has a moderate direct electronic bandgap, with anisotropic mechanical properties. Their elastic modulus ranges between 50 and 62 GPa. The results for optical properties suggest that qHPC$_{60}$ can act as UV collectors for photon energies until 5.5 eV since they present low reflectivity and refractive index greater than one. …
A DFT study of the synthesized MAX phase Zr2SeC has been carried out for the first time to explore its physical properties for possible applications in many sectors. The studied properties are compared with prior known MAX phase Zr2SC. The structural parameters (lattice constants, volume, and atomic positions) are observed to be consistent with earlier results. The band structure and density of states (DOS) are used to explore the metallic conductivity, anisotropic electrical conductivity, and the dominant role of Zr-d states to the electrical conductivity. Analysis of the peaks in the DOS and…
Recently hybridized monolayers consisting of hexagonal boron nitride (h-BN) phases inside graphene layer have been synthesized and shown to be an effective way of opening band gap in graphene monolayers [1]. In this letter, we report an ab initio density functional theory (DFT)- based study of h-BN domain size effect on the elastic properties of graphene/boron nitride hybrid monolayers (h-BNC). We found both inplane stiffness and longitudinal sound velocity of h-BNC linearly decrease with h-BN concentration.
NaSn2P2 is a recently discovered superconducting system belonging to a particular class of materials with van der Waals structure. There is enormous interest in such compounds because of their intriguing electrical, optical, chemical, thermal, and superconducting state properties. We have studied the pressure dependent structural, thermo-physical, electronic band structure, and superconducting state properties of this quasi-two dimensional system in details for the first time via ab initio technique. The optical The optical properties are also investigated for different electric field polariza…
Small system sizes are a well known source of error in DFT calculations, yet computational constraints frequently dictate the use of small supercells, often as small as 96 atoms in oxides and compound semiconductors. In ionic compounds, electrostatic finite size effects have been well characterised, but self-interaction of charge neutral defects is often discounted or assumed to follow an asymptotic behaviour and thus easily corrected with linear elastic theory. Here we show that elastic effects are also important in the description of defects in ionic compounds and can lead to qualitatively i…
The effect of pressure on the structural, elastic and electronic properties of the intermetallic compound MgCu with a CsCl-type structure have been investigated using ab-initio technique. The optical properties have been studied under normal pressure. We have carried out the plane-wave pseudopotential approach within the framework of the first-principle density functional theory (DFT) implemented within the CASTEP code. The calculated structural parameters show a good agreement with the experimental and other theoretical results.
The Zr-based MAX phases have attracted considerable attention for their outstanding irradiation behavior and high neutron transparency relevant to nuclear power generation technologies. In spite of increased understanding of physical behavior crystalline MAX phases, the high-temperature oxidation behavior and reaction mechanism of disordered MAX phases both from theory and experiments are not well understood due to increased system complexity. Here, we present a detailed comparative assessment of high-temperature thermodynamic-stability and oxidation behavior (reaction-products and chemical ac…
Structural, elastic and electronic band structure properties of A-15 type Nb-based intermetallic compounds Nb3B (B = Os, Pt, Au) have been revisited using first principles calculations based on the density functional theory (DFT). All these show excellent agreement with previous reports. More importantly, electronic bonding, charge density distribution and Fermi surface features have been studied in detail for the first time. Vickers hardness of these compounds is also studied. The Fermi surfaces of Nb3B contain both hole- and electron-like sheets, the features of which change systematically a…
Single-crystal elastic moduli, Cij, and the B1-B2 phase transition of NaCl were investigated experimentally, using time-domain Brillouin scattering (TDBS), and theoretically, via density-functional-theory (DFT), to 41 GPa. Thus, we largely extended pressure range where Cij and elastic anisotropy of the solid are measured, including the first experimental data for the high-pressure B2 phase, NaCl-B2. NaCl-B1 exhibits a strong and growing with pressure anisotropy, in contrast to NaCl-B2. Theoretical values obtained using different advanced DFT functionals were compared with our measurements but …
We computed structural, elastic, electronic and optical properties of Be2X(X = C; Si; Ge; Sn) family of antiuorite with ab initio DFT calculations using the generalized gradient approximation (GGA). The different parameters such as geometry optimization, band structure, density of states, elastic constants, dielectric functions have been studied. We also calculated bandgap using PBE0 and HSE hybrid functionals to compare experimental bandgap of Be2C. Although three of the compounds are hypothetical in nature, their formation energy found to be negative. The calculated values of elastic constan…
DFT based investigation of structural, elastic, optoelectronic, thermophysical and superconducting state properties of binary Mo3P at different pressures
First-principles calculations were performed, and the results from the study of structural, electronic and elastic properties of zincblende III-arsenide binary compounds (BAs, AlAs, GaAs and InAs) are presented. These properties have been calculated using an ab initio pseudopotential method based on density functional theory (DFT) with the local density approximation (LDA) for the exchange-correlation potential. The results obtained for the calculated properties have been compared with experimental data and other computational works. It has also been found that our results with LDA are in good…
Tetragonal Mo5PB2 compound, a recently discovered superconductor, belongs to technologically important class of materials. It is quite surprising to note that a large number of physical properties of Mo5PB2, including elastic properties and their anisotropy, acoustic behavior, electronic (charge density distribution, electron density difference), thermo-physical, bonding characteristics, and optical properties have not been carried out at all. In the present work we have explored all these properties in details for the first time with density functional theory based first-principles method. Mo…
The elastic properties of paramagnetic cubic B1 (c-) Cr1-xAlxN ternary alloys are studied using stress-strain and energy-strain methods within the framework of Density Functional Theory (DFT). A strong compositional dependence of the elastic properties is predicted. Young's modulus, E, and shear modulus, G, exhibit the same compositional trends as experimentally measured hardness values (i.e. increasing with Al content), while bulk modulus, B, remains almost constant. The isotropic elastic response in the c-Cr1-xAlxN is predicted for concentrations around x=0.50. Brittle behavior and direction…
The effect of pressure on the zone-center optical phonon modes and the elastic properties of hafnium has been studied by both experimental (Raman scattering) and theoretical (DFT) approaches. It was found an anomaly dependence of the phonon frequency of E$_{2g}$ mode in the pressure range from 0 to 67 GPa. The calculated electronic structure of hafnium shows significant changes under pressure, which have a pronounced spatial anisotropy similar to the anisotropy of the observed phonon properties. The dependencies of the elastic properties on pressure including the components of the elasticity t…
Using the density functional theory (DFT) formulated within the framework of the plane-wave basis projector augmented wave (PAW) method, the temperature-dependent elastic properties of MgRE (RE=Y, Dy, Pr, Sc, Tb) intermetallics with B2-type structure are presented from first-principles. Our calculations are based on the fact that the elastic moduli as a function of temperature mainly results from thermal expansion. The comparison between the predicted results and the available experimental data for a benchmark material NiAl provides good agreements. At $T=0K$, our calculated values of lattice …
Pentadiamond is a recently proposed new carbon allotrope consisting of a network of pentagonal rings where both sp$^2$ and sp$^3$ hybridization are present. In this work we investigated the mechanical and electronic properties, as well as, the thermal stability of pentadiamond using DFT and fully atomistic reactive molecular dynamics (MD) simulations. We also investigated its properties beyond the elastic regime for three different deformation modes: compression, tensile and shear. The behavior of pentadiamond under compressive deformation showed strong fluctuations in the atomic positions whi…
We show that a deep-learning neural network potential (DP) based on density functional theory (DFT) calculations can well describe Cu-Zr materials, an example of a binary alloy system that can coexist in several ordered intermetallics and as an amorphous phase. The complex phase diagram for Cu-Zr makes it a challenging system for traditional atomistic force-fields that fail to describe well the different properties and phases. Instead, we show that a DP approach using a large database with ~300k configurations can render results generally on par with DFT. The training set includes configuratio…
A topological insulator possesses a bulk energy gap splitting the lowest empty band from the highest occupied electronic band. The electronic states at the surface (or edge in two dimensions), on the other hand, of a topological insulator are gapless and are protected by the time reversal symmetry. Such systems are promising for variety of optoelectronic, superconducting, thermoelectric and quantum computation related applications. We have studied elastic, mechanical, electronic, optical properties, bonding character and the electronic charge density distribution of ternary Bi2Te2Se topologica…
Using a synergistic combination of experimental and computational methods, we shed light on the unusual solubility of (Cr,Ti)3AlC2 MAX phase, showing that it may accommodate Cr only at very low concentrations (<2at%) or at the exact Cr/(Cr+Ti) ratio of 2/3, even when the ratio of reactants is far from this stoichiometry (1/2 < Cr/(Cr+Ti) < 5/6). In both phases Cr exclusively occupies the 4f sites, bridging carbide layers with the Al layer. Despite this, the peculiar stability of (Cr2/3Ti1/3)3AlC2 is attributed to the formation of strong, spin-polarised Cr-C bonds, which result in volume reduct…
We have performed ab-initio calculations using plane-wave ultraviolet pseudopotential technique based on the density-functional theory (DFT) to study the structural, mechanical, electronic, optical and thermodynamic properties of orthorhombic MgV2O6. The calculated lattice parameters are in good agreement with the available experimental data. The second-order elastic constants and the other relevant quantities such as the Youngs modulus, shear modulus, Poissons ratio, compressibility, anisotropy factor, sound velocity, and Debye temperature have been calculated. After analyzing the calculated …
We have parameterized a reactive force field (ReaxFF) for lithium aluminum silicates using density functional theory (DFT) calculations of structural properties of a number of bulk phase oxides, silicates, and aluminates, as well as of several representative clusters. The force field parameters optimized in this study were found to predict lattice parameters and heats of formation of selected condensed phases in excellent agreement with previous DFT calculations and with experiments. We have used the newly developed force-field to study the eucryptite phases in terms of their thermodynamic sta…
In this work we present a detailed computational study of structural and elastic properties of cubic AlGaInN alloys in the framework of Keating valence force field model, for which we perform accurate parametrization based on state of the art DFT calculations. When analyzing structural properties, we focus on concentration dependence of lattice constant, as well as on the distribution of the nearest and the next nearest neighbour distances. Where possible, we compare our results with experiment and calculations performed within other computational schemes. We also present a detailed study of e…
In this paper, we have presented the density functional theory (DFT) based calculations performed within the first-principles pseudopotential method to investigate the physical properties of the newly discovered superconductor LaRu2As2 for the first time. The optimized structural parameters are in good agreement with the experimental results. The calculated independent elastic constants ensure mechanical stability of the compound. The calculated Cauchy pressure, Pugh's ratio as well as Poisson's ratio indicate that LaRu2As2 should behave as a ductile material. Due to low Debye temperature, LaR…
The density-functional theory (DFT) and density-functional perturbation theory (DFPT) are employed to study the pressure dependence of elastic and dynamical properties of zinc-blende ZnS and ZnSe. The calculated elastic constants and phonon spectra from 0 GPa to 15 GPa are compared with the available experimental data. Generally, our calculated values are overestimated with experimental data, but agree well with recent other theoretical values. The discrepancies with experimental data are due to the use of local density approximation (LDA) and the effect of temperature. In this work, in order …
Large-scale simulations of plastic deformation and phase transformations in alloys require reliable classical interatomic potentials. We construct an embedded-atom method potential for niobium as the first step in alloy potential development. Optimization of the potential parameters to a well-converged set of density-functional theory (DFT) forces, energies, and stresses produces a reliable and transferable potential for molecular dynamics simulations. The potential accurately describes properties related to the fitting data, and also produces excellent results for quantities outside the fitti…
The elastic properties of eta-Fe2C (eta carbide) have been determined from ab initio density functional theory (DFT) calculations using the generalized gradient approximation (GGA). The isotropic polycrystalline elastic modulus of eta-Fe2C has been calculated as the average of anisotropic single-crystal elastic constants determined from the ab initio simulations. The calculated polycrystalline elastic modulus was used to compute the elastic modulus of a case carburised gear steel subjected to shallow cryogenic treatment (SCT) and deep cryogenic treatment (DCT). This value was then compared wit…
Unlike covalent two-dimensional (2D) materials like graphene, 2D metals have non-layered structures due to their non-directional, metallic bonding. While experiments on 2D metals are still scarce and challenging, density-functional theory (DFT) provides an ideal approach to predict their basic properties and assist in their design. However, DFT methods have been rarely benchmarked against metallic bonding at low dimensions. Therefore, to identify optimal DFT attributes for a desired accuracy, we systematically benchmark exchange-correlation functionals from LDA to hybrids and basis sets from p…
212 MAX phase borides are new additions to the MAX phase family with enhanced thermo-mechanical properties. In this article, first-principles calculations have been carried out to explore the mechanical properties, Vickers hardness, elastic anisotropy, thermal properties, and optical properties of predicted thermodynamically stable MAX compounds Hf2AB2 (A = In, Sn). The structural properties are compared with the available data to assess the validity of calculations. The mechanical stability of Hf2AB2 (A = In, Sn) compounds is established with the help of the computed stiffness constants (Cij)…
In the Letter [J. Nucl. Mater. 444, 356 (2014)] and Comment [Phys Rev B 90, 157101 (2014)], Soderlind et al. argue that 1) DFT based on GGA already models U metal and U-Zr alloy accurately, and 2) DFT + U models them worse than DFT according to results they calculate or select from our recent study [Phys. Rev. B 88, 235128 (2013)]. Here we demonstrate in response to 1) that previously neglected and more recent experimental data indicate that DFT, even when implemented in all-electron methods, does not model the bulk modulus and elastic constants of αU very accurately. Furthermore, Soderlind et…
