Vibrational properties of Ba 1- xK xBiO 3: A molecular dynamics study

Abstract

We present a rigid-ion model of Ba 1- x K x BiO 3 for compositions x=0.25 and x=0.40. Partial vibrational density of states of ions in the compounds Ba 0.75K 0.25BiO 3 and Ba 0.6K 0.4BiO 3 are reported at room temperature and 100 K. The oxygen modes dominate the vibrational spectrum from 150 up to 820 cm -1. The low frequency modes are associated with the cations. The number of substituted K around an oxygen favors high frequency vibrational modes. Qualitative agreement between the calculated phonon density of states of Ba 0.6K 0.4BiO 3 and available experimental data is achieved.