  Hartree-Fock and coupled-cluster calculations have been performed for cubic
AgCl and for AuCl having a cubic or the observed structure with space group
I4_1/amd. Cohesive energies and lattice constants are in excellent agreement
with experiment for AgCl; for AuCl we find good agreement, and the experimental
structure is correctly predicted to be lower in energy than the cubic one.
Electron-correlation effects on lattice constants are very large, of up to 0.8
\AA for cubic AuCl. We especially discuss the strength of the closed-shell
interactions, and for the first time a quantitative analysis of the so-called
"aurophilic" Au(I)-Au(I) interaction is presented in solids.
