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

A Monte Carlo simulation of liquid acetone was performed in the NVT en semble. The dielectric polarizability of the molecules was taken into account by induced point dipoles. A reference simulation on a system o f non-polarizable molecules was also carried out. The induced polariza tion of the molecules lowered the total energy of the system, while th e sum of the pair interaction energies was increased. The structural a nalysis of the resulting configurations revealed that the average coor dination number in the first coordination shell is about 12, and the f irst one or two nearest neighbours tend to be in an antiparallel orien tation relative to the central molecule while the orientation of the r est of the neighbours is random. The predominant interaction in determ ining the structure of liquid acetone was found to be steric rather th an 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 mo ment of the molecules by about 28%. The average angle between the perm anent and induced dipoles was found to be quite large, i.e., 32 degree s. 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.