  We present a comprehensive benchmark study of the adsorption energy of a
single water molecule on the (001) LiH surface using periodic coupled cluster
and quantum Monte Carlo theories. We benchmark and compare different
implementations of quantum chemical wave function based theories in order to
verify the reliability of the predicted adsorption energies and the employed
approximations. Furthermore we compare the predicted adsorption energies to
those obtained employing widely-used van der Waals density-functionals. Our
findings show that quantum chemical approaches are becoming a robust and
reliable tool for condensed phase electronic structure calculations, providing
an additional tool that can also help in potentially improving currently
available van der Waals density-functionals.
