The effective-medium-theory estimate of the binding energy of an atom to a host (another atom, molecule, or solid) from the host electron density, and the binding energy of the atom in a homogeneous electron gas has been extended to include covalent effects. The covalent term involves the difference in the one-electron energies between the atom in the host and the atom in homogeneous electron-gas systems. The scheme is tested for helium impurities in several transition metals and for hydrogen impurities in all the metals from potassium to copper. For helium all available binding energies are well reproduced and all the observed trends in the hydrogen heat of solution can be accounted for.

• Received 18 January 1982

DOI:https://doi.org/10.1103/PhysRevB.26.2875