Contribution of Core Polarization to the Cohesive Energies of the Alkali Metals

An approximate potential is constructed to represent the effect of polarization of the atomic core on the energy of the valence electron in an atom with one valence electron. The potential is proportional to 1R⁴ at large distances from the nucleus, but vanishes at the origin. The potential is treated in first-order perturbation theory to determine its contribution to the cohesive energies of the alkali metals. Numerical calculations have been made for lithium, sodium, and potassium. In the latter element, it represents about 1/3 of the observed cohesive energy.