Abstract The molecular dynamics of CH 2C 2 in the liquid state have been simulated with two model representations of the intermolecular potential. These consist of a three-interaction site model and a five-interaction site one with or without fractional electrical charges at the atomic sites. The MD algorithms used in the simulation are described in detail. Equilibrium thermodynamic properties are calculated and compared with experimental data. In part two some dynamical properties are presented and some attention is given to the reproduction of the experimental far infrared spectra.