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

Abstract

The van Hove scattering function $S(q,\ensuremath{\omega})$ has been measured at 12 state conditions along the 297-K isotherm of krypton gas between 6 and 14\ifmmode\times\else\texttimes\fi{}${10}^{27}$ atoms/${\mathrm{m}}^{3}$ and for the magnitude of the scattering vectors ($\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}$) between 0.4 and 3.3 ${\mathrm{\AA{}}}^{\ensuremath{-}1}$. Integration of the data gives the static structure factors which have a major peak at $q\ensuremath{\simeq}1.8$ ${\mathrm{\AA{}}}^{\ensuremath{-}1}$. 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 $S(q,\ensuremath{\omega})$ 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 $\ensuremath{\omega}$, and for low momentum transfer ($q\ensuremath{\le}1.8$ ${\mathrm{\AA{}}}^{\ensuremath{-}1}$) 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 $\ensuremath{\omega}$ is increased.