Calculated properties of the commensurate monolayers of helium and hydrogen on graphite

Abstract
Calculations of the mean-square lateral displacements and of the Brillouin-zone-center frequency gap are reported for the √3 R30° lattices of helium adsorbed on the basal plane surface of graphite. Results, which depend strongly on the value adopted for the corrugation amplitude in the holding potential, are in good agreement with experimental data. Correction and extension of calculations reported by the authors in Phys. Rev. B 40, 148 (1989) bring the results for hydrogen also into good agreement with experimental data.