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1.
《Intermetallics》2014
The influence of tensile strain in the ab-plane on crystal and electronic structure of FeTe has been studied ab initio. In superconducting FeSe the Fermi surface nesting with a vector q ∼ (0.5,0.5) × (2π/a) is believed to be crucial for rising superconductivity mediated by spin-fluctuations. The results presented here indicate that tensile-strained FeTe also exhibits such conditions. Furthermore, the Fermi surface changes, related to the increase of the lattice parameter a of this telluride, are opposite to analogous effects reported for FeSe. Since a recently transition from the double-stripe to the single-stripe magnetic order in FeTe under tensile strain in the ab-plane is associated with an occurrence of superconductivity in corresponding thin films, these findings allow for drawing a consistent picture of superconductivity in FeSe1−xTex systems, in general. 相似文献
2.
《Intermetallics》2015
Electronic structures of a superconductor without inversion symmetry, LaPdSi3, and its non-superconducting counterpart, LaPdGe3, have been calculated employing the full-potential local-orbital method within the density functional theory. The investigations were focused on analyses of densities of states at the Fermi level in comparison with previous experimental heat capacity data and an influence of the antisymmetric spin–orbit coupling on the band structures and Fermi surfaces (FSs) being very similar for both considered here compounds. Their FSs sheets originate from four bands and have a holelike character, but exhibiting pronounced nesting features only for superconducting LaPdSi3. It may explain a relatively strong electron–phonon coupling in the latter system and its lack in non-superconducting LaPdGe3. 相似文献
3.
《Intermetallics》2014
To improve the performance of a thermoelectric material CuGaTe2, element Ag is doped to replace element Ga and we investigate the electronic structure, phase stability, elastic and thermoelectric properties of CuGa1−xAgxTe2 (x = 0, 0.25 and 0.5) via first-principles method. The phase stability of CuGa1−xAgxTe2 is discussed by analyzing the formation energy, cohesive energy and elastic constants. The calculated sound velocities decrease with the increase of Ag content, which is favorable for reducing the lattice thermal conductivity. The analysis of band structures shows that the replacement of Ga by Ag makes CuGaTe2 undergo a direct-indirect semiconductor transition. The Ag doping induces steep density of states in valence band edge, which is beneficial for increasing the carrier concentration and improving thermoelectric performance of CuGaTe2. 相似文献
4.
《Intermetallics》2015
By the first-principles calculations, we present the results of electronic structure and magnetic properties on bulk CrGa2Sb2 and MnGa2Sb2 in an orthorhombic structure with the linear chains of transition-metal Cr and Mn atoms, using four different exchange correlation potentials: the local density approximation (LDA), the generalized gradient approximation (GGA), GGA + U, and the Tran-Blaha modified Becke-Johnson functional (mBJ). The electronic structure calculations from four exchange correlation potentials show that CrGa2Sb2 is a pseudogap (negative gap) material with very small density of states (DOS) at the Fermi level, while MnGa2Sb2 has notably higher DOS at the Fermi level compared to CrGa2Sb2, exhibiting stronger metallic conductivity, although the mBJ potential obtains lower DOS at the Fermi level than LDA and GGA for both CrGa2Sb2 and MnGa2Sb2. The GGA + U method with a small value (1 eV) of the on-site Coulomb interaction parameter U obtains lower DOS at the Fermi level compared to the large value of U. In agreement with the measurement data, the total energy calculations reveal that both CrGa2Sb2 and MnGa2Sb2 have a stable ferromagnetic ground state with lower energies relative to antiferromagnetic state. Based on the Heisenberg model, the magnetic exchange constants between the nearest-neighbor Cr–Cr and Mn–Mn along transition-metal linear chains are calculated to be 48.6 meV and 27.5 meV for CrGa2Sb2 and MnGa2Sb2, respectively. By the mean-field approximation method, we calculated the Curie temperature of two compounds to be above room-temperature. 相似文献
5.
《Intermetallics》2014
The structural, elastic, thermodynamic and electronic properties of L12-ordered intermetallic compounds Ni3X (X = Al, Ga and Ge) under pressure range from 0 to 50 GPa with a step of 10 GPa have been investigated using first-principles method based on density functional theory (DFT). The calculated structural parameters of Ni3X at zero pressure and zero temperature are consistent with the experimental data. The results of bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio v, anisotropy index AU and Debye temperature ΘD increase with the increase of external pressure. In addition, the Debye temperature of these compounds gradually reduce as the order of Ni3Al > Ni3Ga > Ni3Ge. The ratio of shear modulus to bulk modulus G/B shows that the three binary compounds are ductile materials, and the ductility of Ni3Al and Ni3Ga can be improved with pressure going up, while Ni3Ge is opposite. Finally, the pressure-dependent behavior of density of states, Mulliken charge and bond length are analyzed to explore the physical origin of the pressure effect on the structural, elastic and thermodynamic properties of Ni3X. 相似文献
6.
《Intermetallics》2014
We report the structural, electronic, bonding, elastic and mechanical properties of nine scandium intermetallic compounds, ScTM (TM = Co, Rh, Ir, Ni, Pd, Pt, Zn, Cd and Hg), using ab initio density functional theory with the generalized gradient approximation for exchange and correlation potentials. The calculated structural parameters, such as the lattice constant (a0), bulk modulus (B) and its pressure derivative (B0) and elastic constants, are calculated using the CsCl-(B2 phase) structure. The electronic and bonding properties of the ScX compounds are quantitatively analyzed using band structures, DOS, Fermi surfaces and contour plots. The mechanical properties and ductile behaviors of these compounds are also predicted based on the calculated elastic constants. 相似文献
7.
《Intermetallics》2014
The temperature-dependent structural properties and anisotropic thermal expansion coefficients of α-/β-Nb5Si3 phases have been determined by minimizing the non-equilibrium Gibbs free energy as functions of crystallographic deformations. The results indicate that the crystal anisotropy of α-Nb5Si3 phase is much more temperature dependence than that of β-Nb5Si3 phase. The total/partial density of states of α-/β-Nb5Si3 phases are discussed in detail to analyze their electronic hybridizations. It is demonstrated that the bonding of the two phases is mainly contributed from the hybridization between Nb-4d and Si-3p electronic states. The temperature-dependent mechanical properties of α-/β-Nb5Si3 phases are further investigated via the quasi-harmonic approximation method in coupling with continuum elasticity theory. The calculated single-crystalline and polycrystalline elasticity shows that both phases are mechanically stable and exhibit the intrinsic brittleness. The results also suggest that α-Nb5Si3 phase possesses a superior ability of compression resistance but an inferior ability of high-temperature resistance of mechanical properties than those of β-Nb5Si3 phase. The bonding features of α-/β-Nb5Si3 phases are discussed by means of charge density difference analysis in order to explain the difference of the temperature-dependent mechanical properties between the two phases. 相似文献
8.
《Intermetallics》2014
By means of first principles calculations, we have studied the structural, elastic, and phonon properties of the Al12X (X = Mo, Tc, Ru, W, Re, and Os) compounds in cubic structure. The elastic constants of these compounds are calculated, then bulk modulus, shear modulus, Young's modulus, Possion's ratio, Debye temperature, hardness, and anisotropy value of polycrystalline aggregates are derived and relevant mechanical properties are compared with the available theoretical ones. Furthermore, the phonon dispersion curves, mode Grüneisen parameters, and thermo-dynamical properties such as free energy, entropy and heat capacity are computed and the obtained results are discussed in detail. 相似文献
9.
The influence of structural, elastic properties, thermodynamics and electronic properties Al-Y alloy were investigated by using first-principles. The equilibrium lattice constant, elastic constants, and elastic modulus as calculated here agree with results of previous studies. Calculated results of bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio v and Debye temperature all increase as pressure increase, but the opposite is true for heat capacity cp. In addition, the Debye temperature for the phases reduces gradually as follows: Al2Y > Al3Y> AlY. Additionally, the G/B ratio indicates that AlY and Al3Y are ductile materials, while Al2Y is a brittle material, and that the ductility of AlY and Al3Y can be improved with increased pressure, while the brittleness of Al2Y does not improve with increased pressure. Finally, the paper presents and discusses calculations of density of states and charge populations as they are affected by pressure. 相似文献
10.
《Intermetallics》2014
The structural, elastic and thermodynamic properties of FeB, Fe2B, orthorhombic and tetrahedral Fe3B, FeB2 and FeB4 iron borides are investigated by first-principle calculations. The elastic constants and polycrystalline elastic moduli of Fe–B compounds are usually large especially for FeB2 and FeB4, whose maximum elastic constant exceeds 700 GPa. All of the six compounds are mechanically stable. The Vickers hardness of FeB2 is estimated to be 31.4 GPa. Fe2B and FeB2 are almost isotropic, while the other four compounds have certain degree of anisotropy. Thermodynamic properties of Fe–B compounds can be accurately predicted through quasi-harmonic approximation by taking the vibrational and electronic contributions into account. Orthorhombic Fe3B is more stable than tetrahedral one and the phase transition pressure is estimated to be 8.3 GPa. 相似文献
11.
12.
《Intermetallics》2014
We demonstrate applicability of the proposed extended cluster expansion (CE) technique, enabling complete representation of strain effects on alloy configurational energy on single and multiple lattices. Complete and orthonormal basis function to describe configurational energy is constructed in terms of spin variable ω on virtual lattice and σ on base lattice, where the former specifies the strain of a given cell from the base cell. We estimate formation energy of superlattice composed of alternate stacking of ordered structures for Cu–Au binary alloys where the strain effects should play significant role. The proposed CE is shown to precisely estimate the strain effects on total energy for alloys, which cannot be essentially handled by the current CE. 相似文献
13.
《Intermetallics》2014
Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to calculate structural stabilities, electronic structures, and ferromagnetism of Fe3Si, Fe11NiSi4, Fe11CoSi4 and Fe11CrSi4 intermetallic compound. This study showed that the Fe11NiSi4 and Fe11CrSi4 phase are more stable than Fe3Si phase, especially Fe11NiSi4, but decreased with Fe11CoSi4 phase. Calculating the density of states and the Mulliken electronic populations showed that Fe11NiSi4 had the highest structural stability because of its Fermi level, which was close to the bottom of the pseudo-gap. Fe11NiSi4 also had the largest Mulliken population, which increased the metallic bonding of the alloying system. The total magnetic moments of Fe11NiSi4, Fe11CoSi4 and Fe11CrSi4 were 20.04μB, 19.98μB, and 18.81μB, respectively. These magnetic moments mainly originated from the 3d spin polarization of Fe and those of additional atoms. 相似文献
14.
《Intermetallics》2015
The present work describes the structural and mechanical behaviour of three phases namely B2, D019 and O phases of Ti2AlZr intermetallic using first principles density functional theory (DFT) within generalized gradient approximation (GGA). The equilibrium lattice constant values of B2, D019 and O phases are in good agreement with the experimental and theoretical data, respectively. Formation energy of O phase is minimum followed by D019 and B2. Bonding characteristics of these phases have been explained based on electronic density of states and charge density. All the three phases satisfy the Born stability criteria in terms of elastic constants and are associated with ductile behaviour based on G/B ratios. The B2 phase exhibits very high anisotropy in comparison to those of the D019 and O. 相似文献
15.
N. Novakovi N. Ivanovi V. Koteski I. Radisavljevi J. Beloevi-avor B. Ceki 《Intermetallics》2006,14(12):1403-1410
In order to investigate Hf-TM (TM = Fe, Co, Rh, Ru) phase diagrams in the region of 50:50% atomic ratio, we performed ab initio Full-Potential Linearized Augmented Plane Waves calculations of the most stable Hf and TM elemental phases and HfTM compounds of the CsCl and CuAu structure types. The obtained electronic structures, cohesive energies and enthalpies of formation are discussed and compared to some of the existing models and available experimental data. The non-existing compound HfFe is found to be at least metastable, and the reason for its absence from the phase diagram is discussed. 相似文献
16.
17.
《Intermetallics》2014
Density functional theory and Boltzmann theory calculations of the electronic and thermoelectric properties of Mg2Si subjected to isotropic strains have been performed. The electrical conductivity, the Seebeck coefficient and the power factor have been evaluated at two temperatures (300 K and 900 K) and two charge carrier concentrations (1018 cm−3 and 1.2 × 1020 cm−3 electrons and holes). Up to 3% of both compressive and tensile strains have been applied to the material. From our results, we can highlight that a significant improvement of both the Seebeck coefficient (S) and the power factor (PF) is obtained at low temperature and moderate n-doping. The increase in S and PF amounts to 40% and 100%, respectively, compared to the unstrained Mg2Si. 相似文献
18.
《Intermetallics》2014
We employ density functional theory (DFT) to calculate pressure dependences of selected thermodynamic, structural and elastic properties as well as electronic structure characteristics of equiatomic B2 FeTi. We predict ground-state single-crystalline Young's modulus and its two-dimensional counterpart, the area modulus, together with homogenized polycrystalline elastic parameters. Regarding the electronic structure of FeTi, we analyze the band structure and electronic density of states. Employing (i) an analytical dynamical matrix parametrized in terms of elastic constants and lattice parameters in combination with (ii) the quasiharmonic approximation we then obtained free energies, the thermal expansion coefficient, heat capacities at constant pressure and volume, as well as isothermal bulk moduli at finite temperatures. Experimental measurements of thermal expansion coefficient complement our theoretical investigation and confirm our theoretical predictions. It is worth mentioning that, as often detected in other intermetallics, some materials properties of FeTi strongly differ from the average of the corresponding values found in elemental Fe and Ti. These findings can have important implications for future materials design of new intermetallic materials. 相似文献
19.
《Intermetallics》2014
A systematic investigation on structural, elastic and electronic properties of Rh–Zr intermetallic compounds is conducted using first-principles electronic structure total energy calculations. The equilibrium lattice parameters, enthalpies of formation (Efor), cohesive energies (Ecoh) and elastic constants are presented. Of the eleven considered candidate structures, Rh4Zr3 is most stable with the lowest Efor. The two orthogonal-type, relative to the CsCl-type, are the competing ground-state structures of RhZr. The result is in agreement with the experimental reports in the literature. The analysis of Efor and mechanical stability excludes the presence of Rh2Zr and RhZr4 at low temperature mentioned by .Curtarolo et al. [Calphad 29, 163 (2005)]. It is found that the bulk modulus B increases monotonously with Rh concentration, whereas all other quantities (shear modulus G, Young's modulus E, Poisson's ratio σ and ductility measured by B/G) show nonmonotonic variation. RhZr2 exhibits the smallest shear/Young's modulus, the largest Poisson's ratio and ductility. Our results also indicate that all the Rh–Zr compounds considered are ductile. Furthermore, the detailed electronic structure analysis is implemented to understand the essence of stability. 相似文献
20.
《Intermetallics》2014
The crystal and electronic structures of D8l-V5SiB2 and D88-V5Si3B ternary compounds have been investigated by means of first principle calculations. The calculated structural parameters are in very good agreement with the experimental data. The calculated values of the enthalpies of formation at T = 0 K of the D8l-V5SiB2 and D88-V5Si3B ternary compounds are −67.1 and −62.1 kJ/mol of atoms respectively. The total and partial electronic densities of states show a strong hybridization between the B p states and V d states. The defect enthalpies of formation as well as the mixing enthalpies have been computed. These data are essential for the modeling of the D8l and D88 phases in the V–Si–B ternary system. A partial V–VSi2–VB isothermal section at 298 K is proposed. 相似文献