QUANTUM EFFECTS ON THE HERRINGBONE ORDERING OF N2 ON GRAPHITE

The effects of quantum fluctuations on the ''2-in'' herringbone orderi ng in a realistic model of 900 N2 molecules adsorbed in the (square-ro ot 3 x square-root 3)R30-degrees structure on graphite are studied via path-integral Monte Carlo (PIMC) simulations. Quasiclassical and quas iharmonic calculations agree for high and low temperatures, respective ly, but only PIMC gives satisfactory results over the entire temperatu re range. We can quantify the lowering of the transition temperature a nd the depression of the ground state order to 10% as compared to clas sical modeling.