Multimolecular clusters and their isomerism. Part 14. Breakdown of the conventional formula for the partition function of free internal rotation

Abstract

It has been found that, at low temperatures and small values of the reduced moment of inertia, the conventional formula for the partition function of free internal rotation leads to negative values for the contribution of free internal rotation to the entropy term. It was noted that the reason for this erroneous limiting behavior of the partition function and the thermodynamic functions derived from it lies in the impossibility of approximating the summation through integration under these limiting conditions. An improved formula for the partition function of free internal rotation is suggested, exhibiting correct limiting behavior. The thermodynamics of association of HF and C1F is reevaluated using this new formula, and considerable differences are found compared to the conventional approach.(1) Part 14 in the aeries Multimolecular Clusters and Their Isomerism; for part 13, see ref 21.(2) E.g., N. Davidson, "Statistical Mechanics", McGraw-Hill, New

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