Analysis of scattering data for liquid neon: The isothermal density derivative of the pair correlation function

Abstract

From neutron scattering data for liquid neon we obtain two quantities, the isothermal density derivative of the pair correlation function and the effective pair potential, using a first-principles integral equation which contains systematic corrections beyond the superposition approximation. The calculated density derivative is compared directly with experimental results. The calculated pair potentials at three different densities reflect the statistical fluctuations in the experimental data. They are compared with a fitted potential for neon and with a pair potential obtained by inversion under the superposition approximation. The differences between the two calculations indicate the importance of triplet correlations and the inadequacy of the superposition approximation in these applications, and contribute to an understanding of long-standing doubts concerning the accuracy of effective pair potentials.