Elastic tensor-derived properties of composition-dependent disordered refractory binary alloys

Abstract: The elastic tensor provides valuable insight into the mechanical behavior of a material with lattice strain, such as disordered binary alloys. Density functional perturbation theory (DFPT) based on density functional theory (DFT) provides a powerful mechanism for computing and probing the microscopic features of elastic tensor-related properties. Here we present results for the rigid-ion and relaxed-ion elastic tensors computed using DFPT, for a comprehensive set of structural refractory body-centered cubic (BCC) binary alloys of molybdenum (Mo), niobium (Nb), tantalum (Ta), and tungsten (W). For the first time, we have mapped the heterogeneity in elastic constants and shear modulus and associated relaxation fields at each lattice site by computing the force response internal strain tensor ($\Lambda$) and displacement response internal strain tensors ($\Gamma$). Derived properties -- the bulk modulus ($B$), shear modulus ($G$), Young's modulus ($E$), Poisson's ratio ($\nu$), Pugh's ratio ($B/G$), Cauchy pressure and elastic anisotropy -- are reported as a function of composition for all refractory binaries. The computed mechanical properties data for the refractory binary alloys at systematically-varied Mo, Nb, Ta, and W compositions are in excellent agreement with available experimental data.