MOLECULAR-DYNAMICS STUDIES OF SELF-INTERSTITIALS IN ICE-IH

We carried out molecular dynamics simulations of interstitial water mo lecules in ice to clarify behavior and vibrational properties of self- interstitials in ice. We used an atom-atom potential model developed b y Kumagai er al. [N. Kumagai, K. Kawamura and T. Yokokawa, Mel. Sim. 1 2, 177 (1994)] which allows intramolecular motions. We confirmed high reliability of the potential model for reproducing the structure and v ibrational spectra of ice. From trajectory observations of self-inters titials, we found that a stable interstitial site is an uncapped trigo nal site. By comparing power spectra of vibrational motions for self-i nterstitials with that of matrix ice, we found that the large formatio n entropy of the interstitial molecule is attributed to much higher de nsity of states in a low frequency region for the interstitial than th at for the matrix. (C) 1996 American Institute of Physics.