We present a wave-function-based approach to correlated ab initio calculati
ons on crystalline insulators of infinite extent. It uses the representatio
n of the occupied and the unoccupied (virtual) single-particle states of th
e infinite solid in terms of Wannier functions. Electron correlation effect
s are evaluated by considering virtual excitations from a small region in a
nd around the reference cell, keeping the electrons of the rest of the infi
nite crystal frozen at the Hartree-Fock level. The method is applied to stu
dy the ground-state properties of the LiH crystal and is shown to yield rap
idly convergent results. [S0163-1829(99)15531-0].