Vibrational spectra of hexahalogenometallates. Part II. The infra-red spectra of some cubic and orthorhombic perovskite fluorides

The i.r. spectra of some cubic perovskite fluorides of formulae KMF3(M = Mg, Mn, Fe, Co, Ni, and Zn) and RbMF3(M = Mn, Co, and Zn) have been recorded in the region 40–600 cm–1; from the observed frequencies, a set of five force constants have been calculated. The i.r. spectrum of KMnF3 recorded at liquid-nitrogen temperature is discussed in terms of the reported structural change from a cubic to an orthorhombic or tetragonal phase which occurs at 184 K. The i.r. spectra of the orthorhombic perovskite fluorides NaMF3(M = Mg, Mn, Co, Ni, and Zn) are reported from 40 to 600 cm–1 and the number of observed bands is in good agreement with the predictions of Factor Group Analysis.