Computer simulation of the molecular dynamics of liquid dichloro methane

The molecular dynamics of CH2Cl2 in the liquid state have been simulated with two model representations of the intermolecular potential. These consist of a 3 × 3 and 5 × 5 atom-atom simulation with or without fractional charges at the atomic sites. A variety of thermodynamical and spectroscopic results show that the 5 × 5 potential is the more accurate. The effect of adding charges is significant but not pronounced. For example the simulated far infra-red spectrum looks 15% more like the real thing after an attempt has been made to include charge-charge electrodynamics. It is clear, however, that a better representation of the intermolecular pair potential of CH2Cl2 is needed to match the far infra-red results, and this can probably be obtained by measurements of the second virial of CH2Cl2 over a sufficient temperature range. A coordinated experimental effort is needed to test the wide-range of simulated spectra now available for the asymmetric top CH2Cl2.