How strong is the bond between water and salt?

The interaction of water with salt is central to an almost endless list of scientific areas. However, one of the most fundamental and important questions of how strong the bond is between a water molecule and a salt surface is not yet well-established. Here, we examine water monomer adsorption on the (0 0 1) surface of NaCl with the purpose of obtaining a reliable theoretical estimate of the adsorption energy. The approach followed relies on established quantum chemistry methodologies and involves a separation of the total adsorption energy into contributions from Hartree-Fock and electron correlation, the use of embedded cluster models of the substrate, and extrapolations to the complete basis set limit. Application of this procedure, with electron correlation treated at the CCSD(T) level, yields an adsorption energy for a water monomer on a fixed NaCl(0 0 1) substrate of ≈487 meV and ≈517 meV when substrate relaxations are accounted for.