Hartree-Fock energy bands in molecular crystals : Solid hydrogen in the cubic phase

We calculate the Hartree-Fock energy bands of solid hydrogen in the cubic phase, using a plane-wave-basis set. The novelty of our approach is that, by the expression of the crystal density matrix in terms of localized Gaussian functions, all the matrix elements necessary to calculate the energy bands (including those of the nonlocal exchange operator) can be computed in closed analytical form. This is achieved by the extension to molecular crystals of a technique previously applied to solid rare gases. We compare our results with previous theoretical work, and with available experimental data. In particular, we provide a new interpretation of recent photoemission measurements on thick H2 films deposited on noble metals. The effects of the molecular steric order on the electron states are also briefly discussed