COMPUTER-SIMULATION OF LIQUID METHYL-CHLORIDE

Molecular dynamics and Monte Carlo methods were applied, in the isobar ic-isothermal NPT ensemble to study several thermodynamic states of CH 3Cl in liquid phase. An intermolecular site-site (CH3 and Cl) model wa s used. The thermodynamical properties were studied in the 175 K (mp)- 250 K (bp) range. The calculated densities and vaporization enthalpies for the liquid are in good agreement with experimental results. The a nalysis of the site-site distribution functions indicates the presence in the liquid of some energetically favored relative configurations a s antiparallel and linear dimers. The study of the dynamical propertie s was carried out from the calculation of several time-dependent funct ions as center-of-mass velocities C(v)(t) = [v(t).v(0)], angular C(ome ga)(t) = [J(t)-J(0)], and reorientational C(L)(t) = [P(L)(u(i)(t).u(j) (t))] (L = 1, 2) correlation functions. These functions were used for the calculations of the respective correlation times. The contribution s of the dipolar interactions to the dynamics of liquid CH3Cl were ana lyzed, and it was found that they are modest for the translational but are relevant for the molecular angular velocity correlations. The beh avior of tau(omega) from the mp to the bp shows a small decrease with the temperature. We have observed a fair agreement between simulationa l and experimental results for tau(1), the correlation time related to C1(t). We also provide a comparison of the computer simulation result s with experimental data for the dielectric relaxation of liquid methy l chloride.