Ab initio study of structural, bonding, and vibrational properties of AGaO2 (A = Ag, Cu) delafossites

► An ab initio study of structural and vibrational properties of AgGaO2 and CuGaO2. ► Calculations within the density functional theory and linear response formalism. ► Structural properties of AgGaO2 and CuGaO2 in very good agreement. ► Zone centre phonons in CuGaO2 are in excellent agreement with experiment. ► Calculations predict dynamical instability due to phase transition in AgGaO2.