Short-range order in liquid deuterium under pressure

The structural factor of liquid ortho-deuterium is investigated by neutron diffraction up to 25 A-1 for three values of the density - near the melting curve at pressures of 3.6 and 900 bar and in the vicinity of the critical point. The contributions from intra- and intermolecular correlations are separated out. The radial distribution functions in the liquid and the short-range order structural parameters are determined. It is shown that the variation of the liquid deuterium density near the melting curve under pressure is due to a change in the average distances between the molecules, whereas in the critical region the main effect is a decrease in the mean number of nearest neighbours