Triplet correlation and pair potential functions in liquid neon and sodium

Recent neutron diffraction data for liquid neon and X-ray diffraction data for liquid sodium have been analyzed with the purpose of studying the triplet correlation function in these liquids by means of the method suggested by Egelstaff, Page and Heard. In both cases, it was found that the function H(Q) which expresses the deviation from the superposition approximation indicates the deviation from zero and the effect of the pressure derivative of the structure factor to the function H(Q) is little. Besides, the pair potentials have been investigated from these diffraction data at various pressures using the Born-Green equation. The pair potential functions obtained for three states of liquid neon are the Lennard-Jones type, whereas those obtained for liquid sodium with a provisional assumption based on the experimental data are of the long-range oscillatory type. The pair potentials obtained in this work are useful for the interpretation on the difference in the pressure dependence of the structure factor for liquid neon and sodium.