TRANSFERABILITY AND THE PAIR POTENTIAL WITHIN THE TIGHT-BINDING BOND MODEL - AN ANALYTIC STUDY FOR HYDROGEN

A new analytic tight-binding (TB) pair potential and hopping integral are constructed for hydrogenic s orbitals, by coupling the Harris-Foulkes scheme with Anderson's chemical pseudopotential theory. The validity of using a fixed, transferable TB parametrization is studied and the limitations are found to be twofold. First, although qualitatively reproducing ab initio equilibrium binding energies and atomic separations for diatomic and bulk metallic simple cubic (SC) and face centred cubic (FCC) hydrogen, bulk moduli are globally poorly obtained. This reflects the strong environment dependence of the pair potential and hopping integral. Secondly, errors are incurred by keeping only pairwise terms in a cluster expansion of the exchange-correlation functional. They are found to be non-negligible for bulk systems, being about 25% of the total binding energy for the SC and FCC lattices.