Structural studies of liquid cyclopropane: from room temperature up to supercritical conditions

Abstract

The local order in cyclopropane has been studied using neutron diffraction, in the liquid phase at saturation from room temperature up to temperatures close to the critical temperature and in the supercritical domain under isochoric conditions. A gradual evolution of the structure with the temperature has been evidenced from the experimental pair correlation function d inter(r) and found to involve essentially the two first shells of neighbouring molecules. Upon heating, this residual translational order although weakened as the density decreases is still detected in the hot liquid even at temperatures close to the critical temperature. In the supercritical region the residual local order is found to be more tenuous when increasing the temperature as the density of the fluid is kept constant and equal to the filling density. Finally, the evolution of the local order in cyclopropane in this broad temperature range is discussed using the information taken from molecular dynamics calculations based upon a model developed in a previous study.