Low frequency cation vibrations in high temeprature salt molecules: an evaluation of new experimental data

摘要

High temperature salt molecules have been known for many years, and are known to play a significant role in several high temperature transport and corrosion processes. Accurate thermodynamic modelling of such systems requires knowledge of molecular vibration frequencies, and the initial aim of this paper is to consider the errors in selected thermodynamic parameters arising from uncertainties in low frequency vibrations. This is followed by a presentation of results from recent experiments designed to locate metal-oxygen modes in a variety of high temeprature oxo-anion salt molecules. In particular, matrix isolation far ir studies on alkali metal nitrates show characteristic M-O stretches at ca. 225 and 189 cm~(-1) (M=K), 179 and 144 cm~(-1) (M=Rb), 164 and 130 cm~(-1) (M_Cs). Force constant parameters are evaluated, and the possibility of transferability to other salt molecules is discussed.