On the Calculation of the Force Constants for Halides AX4 n (Td). Using an Empirical Constraint F33 (F2)/F11 (A1) = Constant for Similar Molecules and Ions

Abstract

Abstract An empirical constraint for the determination of the force constants of a General Valence Force Field for the tetrahedral halides with the general formula AX4 n (where A = an element of the groupe II, III, IV, V and VI; X = F, Cl, Br and I and n = +1, 0, -1 and -2) is presented. The model is defined by a constant value of the parameter p= (ft -ftt) / (ft + 3ftt). The optimum value, p = 0.73, obtained for the mixed halides of chlorobromomethane is compared with those calculated from other force fields commonly used.