  Alkali halide (100) surfaces are anomalously poorly wetted by their own melt
at the triple point. We carried out simulations for NaCl(100) within a simple
(BMHFT) model potential. Calculations of the solid-vapor, solid-liquid and
liquid-vapor free energies showed that solid NaCl(100) is a nonmelting surface,
and that the incomplete wetting can be traced to the conspiracy of three
factors: surface anharmonicities stabilizing the solid surface; a large density
jump causing bad liquid-solid adhesion; incipient NaCl molecular correlations
destabilizing the liquid surface, reducing in particular its entropy much below
that of solid NaCl(100). Presently, we are making use of the nonmelting
properties of this surface to conduct case study simulations of hard tips
sliding on a hot stable crystal surface. Preliminary results reveal novel
phenomena whose applicability is likely of greater generality.
