We present a rigid-ion model of Ba, zK,BiO, for compositions x = 0.25 and x = 0.40. Partial vibrational density ot states of ions in the compounds Ba,, ,? K,, ,,BiO, and Ba,, (,Ki, ,BiO, are reported at room temperature and 100 K. The oxygen modes dominate the vibrational spectrum from 150 up to 82Ocm ‘. The low frequency modes arc associated with the cations. The number of substituted K around...