Force Constants and Calculated Thermodynamic Properties for SiF4

Abstract

Using observed fundamental frequencies and the Wilson FG matrix method, sets of force constants for SiF4 have been determined using the most general second degree potential energy function. While no unique set of force constants can be given, limits are set for the force constants. Also the calculations indicate that if the Si–F bond interaction constant is ignored, too high a value for the Si–F bond stretching force constant results. Finally, the heat content, free energy, entropy, and heat capacity for the ideal gaseous state at 1 atmos pressure were calculated for 11 temperatures ranging from 100–1000°K, using a rigid rotator, harmonic oscillator approximation.