EFFECTIVE POTENTIALS FOR LIQUID SIMULATION OF THE ALTERNATIVE REFRIGERANTS HFC-32-CH2F2 AND HFC-23-CHF3

Site-site potentials for use in liquid simulations of difluoromethane and trifluoromethane are constructed using effective interactions. The se rigid molecules have interaction centres at the atomic sites coinci ding with gas-phase monomer geometries, Atomic interactions consist of van der Waals (vdW) and Coulombic parts. The potential functions are adjusted to give simulated liquid properties for temperatures between 0.5 (T/T-C) and 0.9 (T/T-C) on the saturated liquid curves. The propos ed potentials are used in constant pressure-constant temperature (NPT) and constant temperature (NVT) molecular dynamics (MD) simulations of saturated liquid difluoromethane and trifluoromethane. The simulated results of thermodynamic properties and radial distribution functions are compared with experiments where available and the advantages of ou r potential are discussed.