Theoretical research will be done on the structures, excitations and thermal properties of physically adsorbed layers on solid surfaces. Modulated monolayer lattices have domain wall structures with many similarities to structures which occur in the surface reconstructions of metals and semiconductors. The domain wall excitations also have analogies to these systems. Results are used for statistical mechanical evaluation of thermal properties. These phenomena depend on, and provide measures of, the energetic topography of the substrate surface. The substrates treated include: the (111) faces of platinum, palladium, copper, and silver, and the (001) face of magnesium oxide. The primary adsorbates are the inert gas series, helium to xenon. Combinations are chosen which display features present also in more complex systems; quantitative atomic scale models are available or can be constructed by extension of previous work. The work has ties to experiments with x-ray diffraction, thermal neutron scattering, thermal helium scattering, ellipsometry, and microbalances. Theoretical study of the methods for analysing inelastic neutron scattering from commensurate monolayers will also be undertaken. The techniques in this work include lattice dynamical analysis, continuum elasticity theory and variational quantum mechanics. %%%
