Lattice dynamics of ZnAl₂O₄ and ZnGa₂O₄ under high pressure

Abstract

Abstract In this work we present a first‐principles density functional study of the vibrational properties of ZnAl 2 O 4 and ZnGa 2 O 4 as function of hydrostatic pressure. Based on our previous structural characterization of these two compounds under pressure, herewith, we report the pressure dependence on both systems of the vibrational modes for the cubic spinel structure, for the CaFe 2 O 4 ‐type structure ( Pnma ) in ZnAl 2 O 4 and for marokite ( Pbcm ) ZnGa 2 O 4 . Additionally we report a second order phase transition in ZnGa 2 O 4 from the marokite towards the CaTi 2 O 4 ‐type structure ( Cmcm ), for which we also calculate the pressure dependence of the vibrational modes at the Γ point. Our calculations are complemented with Raman scattering measurements up to 12 GPa that show a good overall agreement between our calculated and measured mode frequencies.