Structure determination of liquid argon by x-ray diffraction

Abstract

X-ray diffraction measurements and subsequent data analyses have been carried out on liquid argon at five states in the density range of 0.91–1.35 g/cc and temperature range of 127–143 °K. Duplicate measurements were made on all states. These data yielded radial distribution and direct correlation functions, which were then used to compute the pair potential using the Percus–Yevick and CHNC theories. The potential minima are in the range of −105 to −120 °K, and appear to substantiate current theoretical estimates of the effective pair potential in the presence of a weak three-body force. Numerical experiments on the data have been carried out to study the subsidiary peak phenomenon in the radial distribution function and a distortion phenomenon. The distortion phenomenon for an experiment of the type conducted partially explains why the earlier data by Mikolaj–Pings yielded argon pair potential well depths from the Percus–Yevick equation that were too shallow. The derivation of the correction procedure for distortion is presented.