Study of the structure of molecular complexes. XII. Structure of liquid water obtained by Monte Carlo simulation with the Hartree–Fock potential corrected by inclusion of dispersion forces

Abstract

The two−body Hartree−Fock potential for water−water interaction has been partially corrected by addition of the water−water dispersion interaction recently computed by the Quantum Chemistry Group at the University of Warsaw (Professor W. Kol/os) using a perturbation technique. The new potential has been used in a Monte Carlo simulation of liquid water, where 343 water molecules per unit cell have been considered. The main part of the simulation has been performed at T = 25°C; however, some work is presented for T = 4°C and for T = 75°C. The computed pair correlation functions g_O−O, g_O−H, and g_H−H are in good agreement with the experimental data; agreement is found not only for the main peak of g_O−O at ∼2.9 Å, but also for the second peak at ∼4.5 Å and the third peak at ∼7.0 Å. To further verify the agreement between simulated result and experimental data, we have computed the neutron scattering and the x−ray scattering intensities at different scattering angles. Again the agreement between simulation and experiment is good, thus providing a strong indication that the potential obtained on a quantum−mechanical basis is a realistic one.