MONTE-CARLO SIMULATION OF LIQUID ACETONE WITH A POLARIZABLE MOLECULAR-MODEL

A Monte Carlo simulation of liquid acetone was performed in the NVT ensemble. The dielectric polarizability of the molecules was taken into account by induced point dipoles. A reference simulation on a system of non-polarizable molecules was also carried out. The induced polarization of the molecules lowered the total energy of the system, while the sum of the pair interaction energies was increased. The structural analysis of the resulting configurations revealed that the average coordination number in the first coordination shell is about 12, and the first one or two nearest neighbours tend to be in an antiparallel orientation relative to the central molecule while the orientation of the rest of the neighbours is random. The predominant interaction in determining the structure of liquid acetone was found to be steric rather than electrostatic. The induced dipole moments of the molecules and the electric field strength at the location of the molecular centres were also examined. The induced dipole moment increased the total dipole moment of the molecules by about 28%. The average angle between the permanent and induced dipoles was found to be quite large, i.e., 32 degrees. Neither the magnitude nor the direction of the local electric field strength vector was found to change substantially, on average, by the exclusion of the molecules beyond the first coordination shell.