Electrostatic forces and the frequency spectrum of a monolayer solid of linear molecules on graphite

Electrostatic energies which arise from aspherical atomic charge distributions in a graphite substrate are included in the modeling of a commensurate molecular monolayer. For the planar (two-in) herringbone lattice of nitrogen on graphite such terms may resolve a discrepancy with experimental data for the Brillouin-zone-center frequency gap. The treatment includes consideration of a generalized (two-out) herringbone lattice and of the screening by the graphite of electrostatic fields from the multipole moments of adsorbed molecules. A small adjustment to a previous approximation for the latter process leads to stable modeling of the commensurate monolayer solid of carbon monoxide on graphite.