Perturbation theoretical calculation of the correlation energy in an infinite metallic hydrogen chain

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Abstract
The electronic correlation energy has been calculated in an infinite metallic hydrogen chain using second-order Moller-Plesset perturbation theory and a restricted Hartree-Fock zeroth-order Hamiltonian. The influence of the size of the atomic basis set has been investigated and found to be much more decisive for correlation studies than for the one-particle model. The method that accounts for about 70 per cent of the correlation energy in the molecular case results in -0.626 eV/electron for the infinite chain. The equilibrium lattice distance is only slightly enlarged due to correlation by the cohesion energy is substantially increased. Adding to its value of 1.618 eV/atom, obtained in the present work, the estimated missing correlation part of 0.3 eV, the authors have found that the Hartree-Fock theory accounts for only half of the real cohesion in this solid.