Molecular dynamics study of neutral and charged water clusters

The molecular dynamics calculations of stable geometries and energy parameters of neutral (H2O)n (n ⩽ 100), positively H+(H2O)n and negatively HO−(H2O)n (n ⩽ 15) charged clusters have been carried out within the framework of the Stillinger–David polarization model. Using the results, the size dependences of the energy of the polar fragmentation (H2O)n → H+(H2O)i + HO−(H2O)j have been calculated. The dynamics of collisions between (H2O)27 clusters with the relative velocities of 1, 3, and 10 km/s has been studied. The formation of hydrated ion pairs H+ and OH− was detected, and time dependences of the number of ion pairs, rotational and vibrational temperatures of molecules were obtained. It has been found that both the excitation of molecules in cluster collisions and the dissipation of the hydration energy of ions H+ and OH− have the nonequilibrium character.