  We propose a lattice density-functional theory for {\it ab initio} quantum
chemistry or physics as a route to an efficient approach that approximates the
full configuration interaction energy and orbital occupations for molecules
with strongly-correlated electrons. We build on lattice density-functional
theory for the Hubbard model by deriving Kohn-Sham equations for a reduced then
full quantum chemistry Hamiltonian, and demonstrate the method on the potential
energy curves for the challenging problem of modelling elongating bonds in a
linear chain of six hydrogen atoms. Here the accuracy of the Bethe-ansatz
local-density approximation is tested for this quantum chemistry system and we
find that, despite this approximate functional being designed for the Hubbard
model, the shapes of the potential curves generally agree with the full
configuration interaction results. Although there is a discrepancy for very
stretched bonds, this is lower than when using standard density-functional
theory with the local-density approximation.
