Translational dynamics of a cold water cluster in the presence of an external uniform electric field

Molecular dynamics simulations for a TIP4P water cluster consisting of 32 molecules at T=200 K, under the influence of a broad range of constant electric fields (0.5–7.0×107 V/cm), are presented. This work focuses on the evolution of the single particle translational dynamics, mainly along the field axis as the field is progressively increased, by means of mean-square-displacement curves, the self-part of the van Hove distribution functions and the intermediate scattering functions. Two critical fields have been identified, the one, (EC1=1.5×107 V/cm) assigned to the onset of the dipole alignment and the second one (EC2=5.0×107 V/cm) to the onset of crystallization. These transitions are marked by an abrupt increase of the corresponding structure relaxation times, which remain nearly constant for electric fields between EC1 and EC2. Structure relaxation has been found to obey stretched exponential dynamics, whereas the Q dependence of the relaxation times, for all fields, followed a power law. Fields weaker than EC1 have been found to induce a weakening of the molecular interactions. In this case, the system develops a dynamic behavior similar to that met in the liquid.