An Effective Pair-Potential Study of the Interaction of a Water Monomer with the Basal-Plane Surface of Ice Ih

• Published in: Journal of Glaciology
• Main Authors: Hale, B. N., Kiefer, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1978
• Subjects: Earth-Surface Processes; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/s0022143000033918; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000033918

Abstract The central-force effective pair potential of Rahman and others (1975) is used to generate minimal binding-energy surfaces and configurations of a water monomer adsorbed on the unrelaxed basal plane surface of ice Ih. In the initial study H 2 O molecules arc placed with oxygen atoms fixed at the ice Ih lattice positions and associated hydrogens along the tetrahedral bond directions—restricting the H-O-H bond angles to 109.5°. A rigid-body water monomer adsorbed on the surface interacts with all the H 2 D molecules in the bulk ice model via the central-force effective pair potential. The center-of-mass height, z , and the dipole orientation of the adsorbed H 2 O molecule are varied to minimize the total binding energy of the monomer over a particular ( x,y ) point of the surface. Preliminary results showed that a rigid adsorbed monomer with an H-O-H angle fixed at 104.5° produced only minor deviations in the binding-energy surfaces and that a large bulk-ice model (486 molecules) gave effectively the same results as a smaller ice model (50 molecules). Studies on an infinite ice surface using periodic boundary conditions are in progress and will be used to study surface relaxation and long-range effects on the minimal energy surfaces. Three types of sites on the basal plane were considered: (1) a site with all surface molecule protons pointing out of the surface; (2) a site with all surface molecule protons pointing into the surface; and (3) a site with all rows of surface molecule protons pointing alternately into and out of the surface. A "site" generally refers to a region (about 90 Å 2 ) on the surface over which the minimal binding-energy surface is to be determined. Minimal binding-energy surfaces for the sites have been obtained together with plots showing the surface of the position of the center of mass as a function of x and y . This is a model calculation and is limited by the validity of the potential under close scrutiny. However it gives a qualitative picture of how complex a terrain the real ...