The calculations of absolute entropy. Gaussian vs. “classical” calculation by method of statistical thermodynamics

Abstract

Th e absolute entropy values at 298.15 K of several oxygen and nitrogen-containing organic compounds were calculated within the rigid rotator -harmonic oscillator approximation using various methods of quantum chemistry incorporated in the Gaussian 09 software package. Th e obtained values have been compared with the ones from published sources. Th e impact of the computing method (HF, B3LYP, MP2) and the basis set (6-31G(d,p), 6-311++G(3df,3pd), aug-cc-pvtz) on the accuracy of obtained absolute entropy values has beendiscussed. p) is the most optimal combination of the computing method/utilized basis set for a fast estimation of the entropy values of small organic compounds.