Cunjuan Xia

Structural, elastic and thermodynamic properties of A15-type compounds V3X (X = Ir, Pt and Au) from first-principles calculations

The structural, elastic and thermodynamic properties of the A15 structure V3Ir, V3Pt and V3Au were studied using first-principles calculations based on the density functional theory (DFT) within generalized gradient approximation (GGA) and local density approximation (LDA) methods. The results have shown that both GGA and LDA methods can process the structural optimization in good agreement with the available experimental parameters in the compounds. Furthermore, the elastic properties and Debye temperatures estimated by LDA method are typically larger than the GGA methods. However, the GGA methods can make better prediction with the experimental values of Debye temperature in V3Ir, V3Pt and V3Au, signifying the precision of the calculating work. Based on the E–V data derived from the GGA method, the variations of the Debye temperature, coefficient of thermal expansion and heat capacity under pressure ranging from 0 GPa to 50 GPa and at temperature ranging from 0 K to 1500 K were obtained and analyzed for all compounds using the quasi-harmonic Debye model.

Phase stability, elastic and electronic properties of Hf–Rh intermetallic compounds from first-principles calculations

The phase stability, elastic and electronic properties of binary Hf–Rh compounds have been studied using first-principles calculations based on density functional theory. The equilibrium lattice constants, formation enthalpies, elastic constants, and elastic moduli are presented. Among the binary Hf–Rh compounds, Hf3Rh5 is the most stable with the lowest formation enthalpy. For the equiatomic HfRh phase, it tends to crystallize in the ZrIr-type structure, followed by L10, and then B2 at the ground state based on the analysis of formation enthalpies. Therefore, the crystal structure of the lower temperature HfRh phase is suggested to be the ZrIr-type. This conclusion is in agreement with the experimental reports in the literature. Besides, Hf3Rh4 are proposed to be the Pu3Pd4-type for the first time. Furthermore, our calculated elastic constants for Hf2Rh, ZrIr-HfRh, L10-HfRh, B2-HfRh, Hf3Rh4, Hf3Rh5 and HfRh3 can all satisfy the Born criteria, indicating their mechanical stabilities. When ZrIr-HfRh is adopted, the bulk modulus (B) increases linearly with the growing Rh atomic concentration. Meanwhile, Youngs modulus linearly increases with growing shear modulus, and the compound with a higher Poissons ratio owns a higher B/G ratio simultaneously. Overall, the results also indicate that all the considered Hf–Rh compounds should be ductile. Finally, the electronic structure is analyzed to understand the essence of structural stability of the binary compound.