The structure of the elements in the liquid state

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Abstract
It is by now well established that the structures of the elements in the liquid state follow characteristic trends reminiscent of the trends among the crystal structures of the elements. The crystal structures have been discussed very recently by Hafner and Heine (1983) in terms of the systematic variations of the effective interatomic pair potentials with electron density and pseudopotential. The present analysis of the liquid structures is based on the same set of interatomic potentials and on the optimised random-phase approximation (ORPA) for the calculation of the liquid structure. The authors show that the structural trends in the liquid and crystalline states have the same physical origin. The complex structures of the light polyvalent liquid metals (Ga, Si, Ge) are shown to arise from the interplay of two characteristic distances: the effective diameter of the hard repulsive core expressing the geometrical requirements of sphere packing and the Friedel wavelength of the oscillatory part of the potentials characterising the electronic effects in the metallic bonding. The return to hard-sphere-like structures for the heavy elements stems from the disappearance of the leading term of the Friedel oscillations as the core radius Rc approaches a value for which 2kFRc=1/2 pi .