Overlap Interaction of Water Molecules

摘要

The densehyphen;phase ice VII has special features that enable its equilibrium lattice constant under pressure, internal energy relative to ice I, and compressibility to be calculated readily by means of the vibrational Miemdash;Gruuml;neisen equation of state and the integral and derivative thereof. Experimental values or estimates for these quantities allow evaluation of the overlap energy between neighboring water molecules that are not hydrogen bonded to one another. The result is sensitive to the assumed strength of the van der Waals attraction, which cannot be evaluated independently, but in any case it conflicts with secondhyphen;virialhyphen;coefficient interpretations in indicating a relatively greater overlap repulsion. Experimental evidence from ice VII (quenched) at atmospheric pressure, and from ice II, tends to support a van der Waals interaction at least 50 greater than given by a standard semiempirical version of the London formula. The results enable the stability of Ice VII at very high pressures (sim;200 kbar) to be discussed.