Taking into account anharmonic vibrations in calculations of gas thermodynamic functions

The potential energy of a model operator of vibrational energy of a molecul e includes Morse-type analytic functions, periodic with respect to the tors ion angle for torsional vibrations. This periodic potential is obtained fro m the quasi-one-dimensional section of the potential energy surface. A meth od for calculating corrections for anharmonic effects to thermodynamic func tions, which is, in particular based on Fade approximants, is suggested. It is shown that the magnetic and other characteristics of a substance in the gas phase can change as temperature increases in conformity with the condi tion of thermodynamic stability.