Influence of Pressure on Optical Transparency and High Electrical Conductivity in CoVSn Alloys: DFT Study

Abstract

First-principles calculations of the mechanical, thermal, electronic, optical and transport behavior of CoVSn half-Heusler alloys under external pressure are investigated using density functional theory. The elastic constants and thermoelectric properties are computed using ElaStic and BoltzTrap codes, respectively. The lattice constant and bond lengths are found to decrease with increased pressure. The calculated elastic properties reveal that the CoVSn alloy is mechanically stable and anisotropic under ambient pressure. At 20 GPa, the alloy is shown to be ductile, while at all other pressures it exhibits a brittle nature. In addition, it shows decreased phonon–phonon coupling with an increase in pressure. Using the modified Becke–Johnson (mBJ) potential, it was found that the indirect (L–X) band gap values range from 0.89 eV to 1.00 eV, which agrees with previous studies. The increase in the external pressure directly increases the trend in the band gap while it decreases the static reflective index values. All our calculated optical parameters for the CoVSn alloy are shifted to a high energy level due to the external pressure. Our thermoelectric results suggest that holes are the major charge carriers in the CoVSn alloy. In light of our results, we expect promising optical and thermoelectric applications for CoVSn under pressure.