Lattice dynamics of thin layers of molecular nitrogen adsorbed on graphite.

Abstract

Monolayer and bilayer solid lattices of molecular nitrogen adsorbed on the basal plane surface of graphite are modeled with realistic intermolecular-potential models, and the Helmholtz free energy is evaluated with quasiharmonic lattice dynamics. The stability of herringbone and pinwheel orderings of the layers relative to each other and to the low-temperature three-dimensional solid is determined. There is good agreement with the observed length and energy scales of the monolayer and bilayer lattices. The modeling is consistent with the following succession of lattices: commensurate monolayer herringbone, uniaxially incommensurate monolayer herringbone, monolayer pinwheel, and bilayer pinwheel or bilayer uniaxially incommensurate herringbone.