Exploring the Electronic, Magnetic, Optical, and Thermoelectric Properties of Mn3Si2Te6 by Using the Strain Effect: A DFT Study

Abstract

We performed first-principles calculations to investigate the structural, electronic, magnetic, optical, and thermoelectric properties of Mn₃Si₂Te₆ (MST) at various temperatures using the BoltzTraP package. From the experimental analysis, the material exhibited a metallic nature due to zero bandgap. After performing density functional theory calculations by applying strain engineering on the MST compound, we discovered that the material was a half-metal. The thermoelectric characteristics of the MST compound under strain engineering were investigated using WIEN2k code. The results demonstrated that at 5% tensile strain engineering, the material was half-metal, with an indirect bandgap of 0.732 eV at the Γ–K symmetry point of the Brillouin zone with the generalized gradient approximation (GGA). It was discovered that compressive strain reduced the bandgap whereas tensile strain increased the bandgap value of the bulk MST. With the use of the hybrid functional (GGA + modified Becke–Johnson [mBJ] potential) at 4% tensile strain, the highest bandgap of 1.24 eV at Γ–K was obtained. The optical characteristics at 4% tensile strain were calculated with the hybrid functional. Finally, the thermoelectric properties of MST were determined, including the Seebeck coefficient, electrical conductivity, thermal conductivity, power factor, and figure of merit at 4% tensile strain from 300 K to 800 K. It was found that the Seebeck coefficient and electrical conductivity of MST are temperature-sensitive and decrease as the temperature rises. The Seebeck coefficient was measured at a temperature of 300 K for 4% strain, obtaining values of 300 µV/K (p-type) and 310 µV/K (n-type) region. The lattice thermal conductivity (LTC) was calculated with increasing temperature for MST from 8 W/mK at 100 K to 2 W/mK at 600 K, for 0–10 GPa. The calculated dimensionless figure of merit, ZT, at 300 K reached 0.72 for both p- and n-type, which decreased to 0.56 with experimental thermal conductivity. These results indicate that MST could be suitable material for use in future thermoelectric devices.