Pressure-induced influence on the crystal structure, electronic structure and thermoelectric properties of NaB3: A first-principles study

The pressure-induced modifications in the crystal structure, electronic structure, phonon properties, and thermoelectric properties of NaB3 have been systematically studied by using the first-principle methods and Boltzmann transport theory. Our calculations indicate a phase transition from the low-pressure P4/mbm structure to an orthorhombic Cmmm phase at 23.4 GPa. Two structures are semiconductors and have similar electronic dispersion showing the light band mixing with heavy band, which can be considered as a potential candidate for thermoelectric materials. The further thermoelectric transport calculations show a pronounced anisotropy depending on the crystallographic orientation. The Cmmm structure can exhibit a high thermoelectric performance at high pressure via small p-type doping with a chemical potential around −0.1 eV.