  Mn3TeO6 (MTO) has been experimentally found to adopt a P21/n structure under
high pressure, which exhibits a significantly smaller band gap compared to the
atmospheric R-3 phase. In this study, we systematically investigate the
magnetism, structural phase transition and electronic properties of MTO under
high pressure through first-principles calculations. Both R-3 and P21/n phases
of MTO are antiferromagnetic at zero temperature. The R-3 phase transforms to
the P21/n phase at 7.58 GPa, accompanied by a considerable volume collapse of
about 6.47%. Employing the accurate method that combines DFT+U and G0W0, the
calculated band gap of R-3 phase at zero pressure is very close to the
experimental values, while that of the P21/n phase is significantly
overestimated. The main reason for this difference is that the experimental
study incorrectly used the Kubelka-Munk plot for the indirect band gap to
obtain the band gap of the P21/n phase instead of the Kubelka-Munk plot for the
direct band gap. Furthermore, our study reveals that the transition from the
R-3 phase to the P21/n phase is accompanied by a slight reduction in the band
gap.
