STRUCTURE AND LATTICE-DYNAMICS OF O-H2 AND P-D2 MONOLAYERS ON GRAPHITE

[摘要] Using the H-2-H-2 potential from ab initio calculations and the isotropic H-2-graphite potential from selective adsorption measurements, we have calculated the stability and lattice dynamics of o-H-2 and p-D2 monolayers on graphite. An anisotropic H-2-graphite potential was modelled such that either the herringbone or the pinwheel ordering of the adsorbed layers is stable, at very low temperature. For both these orientationally ordered overlayers we have computed the phonon and libron band structure by the time-dependent Hartree method. We find small coupling between the translational phonons and the librons, which can be well taken into account by renormalisation of the appropriate coupling constants. In the pinwheel structure, observed for o-H-2 monolayers by NMR, the differences between the axial and the wheel molecules are considerably smaller than in the corresponding structure for N2 layers on graphite.

[发布日期] 1991-12-01