Quantum mechanical calculations of molecular properties and ideal gas heatcapacity of difluoromethane

Ideal gas heat capacities are important for the calculation of caloric prop erties of real fluids. But as shown in the past, they are not always availa ble with required accuracy or are still lacking. In this paper, we combine quantum mechanical calculations and statistical thermodynamics. In order to find a route to a reliable prediction of ideal gas heat capacity data, we applied various quantum mechanical methods differing by computational effor t to difluoromethane (CH2F2). Only the structural formula and fundamental p hysical constants enter into the calculations. It is shown that quantum mec hanics leads to accurate molecular data. Reliable experimental heat capacit y data reveal that an accuracy of better than 0.5% is obtained for the idea l gas heat capacity of difluoromethane. (C) 2000 Elsevier Science B.V. All rights reserved.