First-principles study on structural, electronic, elastic, phonon, and thermodynamic properties of tungsten oxide-based perovskite NaWO3

Abstract

The structural, electronic, elastic, phonon, and thermodynamic properties of the cubic perovskite structure of the NaWO3 compound were calculated from first-principles studies based on density functional theory (DFT). These properties were computed within localized density approximation (LDA). The lattice constant (a) and bulk modulus (B) for NaWO3 are found as 3.857 angstrom, 225.314 GPa, respectively. The band structure displayed that the NaWO3 compound exhibits metallic behavior at zero pressure. For elastic properties, elastic constants (C-ij), isotropic shear modulus (G), Young's modulus (Y), Poisson's ratio (v), and anisotropy factor (A) were studied. At zero pressure, the calculated C-11, C-12, and C-44 are 558.933, 88.681, and 66.245 GPa, respectively. According to the results, NaWO3 is mechanically stable. A is not equal to 1. This reveals that NaWO3 is an anisotropic compound. Because of the Cauchy pressure and B/G ratio, NaWO3 behaves ductilely. The shear constants (C-12 and C-44) are less sensitive to pressure than C-11 which indicates little resistance to shear deformation. The negative phonon frequencies were observed in phonon dispersion curves. Therefore, NaWO3 is dynamically unstable. Finally, heat capacity (C-V), entropy (S), and Helmholtz-free energy (F) were also calculated and discussed at 0-1000 K. Consequently, NaWO3 is a potential candidate for future new device designs.