Effects of translational and rotational degrees of freedom on the properties of model water

• Main Authors: T. Mohorič, B. Hribar-Lee, V. Vlachy
• Format: Article
• Language: English
• Published: Institute for Condensed Matter Physics 2015-03-01
• Series: Condensed Matter Physics
• Subjects: water structure; degrees of freedom; molecular dynamics
• Online Access: http://dx.doi.org/10.5488/CMP.18.13004

Molecular dynamics simulations with separate thermostats for rotational and translational motions were used to study the effects of these degrees of freedom on the structure of water at a fixed density. To describe water molecules, we used the SPC/E model. The results indicate that an increase of the rotational temperature, T_R, causes a significant breaking of the hydrogen bonds. This is not the case, at least not to such an extent, when the translational temperature, T_T, is raised. The probability of finding an empty spherical cavity (no water molecule present) of a given size, strongly decreases with an increase of T_R, but this only marginally affects the free energy of the hydrophobe insertion. The excess internal energy increases proportionally with an increase of T_R, while an increase of T_T yields a much smaller effect at high temperatures. The diffusion coefficient of water exhibits a non-monotonous behaviour with an increase of the rotational temperature.