Two-body time correlations in (and the structure of) dense krypton gas

Abstract

The van Hove scattering function $S(q,\omega )$ has been measured at 12 state conditions along the 297-K isotherm of krypton gas between 6 and 14×${10}^{27}$ atoms/${\mathrm{m}}^3$ and for the magnitude of the scattering vectors ($\overrightarrow{\mathrm{q}}$) between 0.4 and 3.3 ${\mathrm{\AA }}^{-1\mathrm{}}$. Integration of the data gives the static structure factors which have a major peak at $q\simeq 1.8$ ${\mathrm{\AA }}^{-1\mathrm{}}$. These data are compared to Monte Carlo calculations with the use of the pair potential for krypton, and differences due to many-body forces are observed. Then the $S(q,\omega )$ functions are compared to hardsphere molecular-dynamics simulations and the predictions of the kinetic theory of gases. Data are presented as a function of $q$ for fixed $\omega$, and for low momentum transfer ($q\le 1.8$ ${\mathrm{\AA }}^{-1\mathrm{}}$) significant differences are observed, while for higher momentum transfer the hard-sphere results are in reasonable agreement with the data. Diffraction maxima are observed for energy transfers up to 3 meV with the peak position moving to higher $q$ as $\omega$ is increased.