Momentum-space formalism for the total energy of solids

A momentum-space formalism for calculating the total energy of solids is derived. This formalism is designed particularly for application with the self-consistent pseudopotential method. In the present formalism, the total energy is obtained through band-structure calculations without involving additional integrations. The Hellman-Feynman theorem is derived, as is a modified virial relation for the pseudopotential Hamiltonian which provides an alternative way of calculating forces and total energies.