Structural stability, phase transition, electronic, elastic and thermodynamic properties of RuX (X = Si, Ge, Sn) alloys under high pressure

Abstract

To understand the RuX(X = Si, Ge, Sn) alloys under high-pressure and high-temperature environment, the structural stability, phase transition, electronic, elastic and thermodynamic properties with CsCl-type (Pm-3m) and FeSi-type (P213) cubic structures have been investigated. Specifically, the calculated basic physical parameters, e.g., lattice constants and bulk modulus, were much closer the experiments than other theoretical data. By contrasting the structural stability, P213>Pm-3m and RuSi > RuGe > RuSn were found, according well with the experiments. Two structural phase transition from P213 to Pm-3m occurs at 0.28 GPa for RuSi and 6.27 GPa of RuGe, in perfect agreement with the experimental results. The electronic properties show that the P213 RuX structures are semiconductors with narrow band gaps, and all Pm-3m structures are metal. In combination with the phase transition and electronic distribution, we found that the P213 RuSn might be instable in the possible pressure range. The elastic constants, shear modulus, Young's modulus, Poison's ratio and Zener anisotropy factor were predicted. The obtained thermodynamic properties, including the heat capacity and thermal expansion coefficient, were well consistent with the experimental values in the ranges from 310 to 1080 K, and further provided in the wide ranges of 0–1800 K with the variations of temperatures and pressures.