Structure factor and electronic structure of compressed liquid rubidium

We have applied the quantal hypernetted-chain equations in combination with the Rosenfeld bridge functional to calculate the atomic and the electronic structure of compressed liquid rubidium under high pressure (0.2, 2.5. 3.9, and 6.1 GPa); the calculated structure factors are in reasonable agreement with experimental results measured by Tsuji et nl. along the melting curve as a whole. It is found that the effective ion-ion interaction is practically unchanged with respect to the potential at room pressure under these high pressures. All structure factors calculated for this pressure-variation coincide almost into a single curve if wave numbers are scaled in units of the Wigner-Seitz radius a although no corresponding scaling feature is observed in the effective ion-ion interaction. This scaling property of the structure factors signifies that the compression in liquid rubidium is uniform with increasing pressure; in absolute Q values this means that the first peak position ce,, of the structure factor increases proportionally to V-1/3 (V bring the specific volume per ion), as was experimentally observed by Tsuji et al. Obviously, this scaling property comes from a specific feature characteristic for effective ion-ion potentials of alkali liquids. We have examined and confirmed this feature for the case of a liquid-lithium potential: starting from the liquid-lithium potential at room pressure we can easily find two sets of densities and temperatures for which the structure factors become practically identical, when scaling Q in units of a.