First-principles study on the electronic structure, phonons and optical properties of LaB₆ under high-pressure

The electronic structure, phonons and optical properties of LaB₆ compound under different pressure have been studied by first-principles calculation. The electronic structure calculation shows that the d band along the M-Γ direction of the Brillouin zone moves up with increasing pressure and the band minimum is above the Fermi level at 45 GPa. The pressure-induced charge transfer from La to B atoms is reflected in the upshift of d band along the M-Γ direction with pressure. The calculated phonon dispersion curve at zero pressure is in good agreement with the experimental results. However, the phonon dispersion under high pressure does not show any information about the phase transition at 10 GPa, which was reported previously. The acoustic and optical phonon modes harden all the way with increasing pressure. In addition, the dielectric function is in accordance with the Drude model in the pressure range of 0 GPa–35 GPa and follows the Lorentz model at 45 GPa. The LaB₆ compound exhibits better visible light transmittance performance with the increasing pressure in the range of 0 GPa–35 GPa and visible light transmittance peak would be shifted towards ultraviolet region. - Highlights: • Physical properties of LaB₆ under high pressure have been theoretically studied. • Predict an electronic topological transition occurs at 45 GPa for LaB₆. • Predict a pressure-induced charge transfer from La to B atoms. • The phonon modes at Γ point show an increasing trend with increasing pressure. • The LaB₆ exhibits better heat-shielding performance with the increasing pressure.