Investigation of the Structural, Electronic and Mechanical Properties of Type-VIII Ba8Si46 Clathrate under High-Pressure through First-Principles

摘要

By means of density functional theory (DFT) calculations, we have systematically investigated the effect of hydrostatic pressure on the structural, electronic and elastic properties of barium-doped silicon clathrate Ba8Si46 in the type-VIII structure (alpha phase). Physical properties are calculated under different conditions of pressure (0 GPa to 45 GPa) using the GGA-PBE functional. Those calculations have been performed using the Cambridge serial total energy package CASTEP within the Materials Studio package. Electronic properties have shown that type-VIII Ba8Si46 has metal-like properties with a fundamental bandgap of 1 eV. Under pressure the fundamental bandgap increases slightly and the positions of the valence band maximum VBM and the conduction band minimum CBM remain unchanged when pressure is changed from 0 to 25 GPa, but when pressure is set to 30 GPa the CBM is transited from its initial position (Gamma-H segment) towards the Gamma(0,0,0) point, this indicates that the bandgap nature of this material can be tuned through strain engineering. We found that the compound is mechanically stable under the pressure range and might be unstable or collapse when pressure exceeds 44 GPa. These findings need to be confirmed experimentally through synthesis, a comparison with the type-I and the guest-free counterparts has exhibited promising features for the type-VIII Ba8Si46.