Quantum effects on the herringbone ordering ofN2on graphite

Abstract
The effects of quantum fluctuations on the ‘‘2-in’’ herringbone ordering in a realistic model of 900 N2 molecules adsorbed in the (√3 × √3 )R30° structure on graphite are studied via path-integral Monte Carlo (PIMC) simulations. Quasiclassical and quasiharmonic calculations agree for high and low temperatures, respectively, but only PIMC gives satisfactory results over the entire temperature range. We can quantify the lowering of the transition temperature and the depression of the ground state order to 10% as compared to classical modeling.