THE EFFECTIVE PAIR POTENTIAL OF EXPANDED LIQUID CESIUM OBTAINED BY THE INVERSE METHOD

The effective pair potentials phi(r) of liquid caesium for a wide rang e of density are derived from experimental structure factors using the inverse method, which is based on the integral equation theory and th e molecular dynamics (MD) simulation. The results are discussed in com parison with those obtained previously for liquid rubidium and with th ose obtained by the pseudopotential perturbation theory. The density d ependence of phi(r) derived for liquid caesium shows features in commo n with that for liquid rubidium: with decreasing density, the repulsiv e part of phi(r) becomes softer, its oscillation becomes smaller and t hen disappears and the resulting attractive part grows longer ranged. It is shown by comparing the corresponding states with the same scaled densities that the repulsive part of the phi(r) for caesium is softer than that for rubidium.