Many-body interaction effects on the low-k structure of liquid Kr

Neutron diffraction measurements and theoretical calculations of the structure factor $S(k)$ of liquid Kr are extended to small k values $(kl4 {\mathrm{nm}}^{\ensuremath{-}1}).$ The results show that many-body interaction contributions have an increasing effect on $S(k)$ as $\stackrel{\ensuremath{\rightarrow}}{k}0,$ reaching at least 40% of the measured intensity. Both the phase diagram and the low-$k$ structural data of dense Kr turn out to be closely reproduced by the hierarchical reference theory if additional many-body forces are taken into account by an augmented strength of the Axilrod-Teller triple-dipole potential. The experimental density derivative of $S(k)$ is also used for a very sensitive test of the theories and interaction models considered here.