High pressure neutron diffraction on fluid propane and a mixture of propane and methane

High pressure neutron diffraction data on deuterated propane at four superc ritical states and on a mixture of 39.93 mole % deuterated propane and 60.0 7 mole % deuterated methane at two supercritical states are presented. In t he case of propane the density could be varied by a factor larger than 2. T he molecular structures of deuterated propane and deuterated methane were d etermined. The density dependence of the intermolecular structure is used i n order to test various united-atoms potential for propane in Monte Carlo s imulations. The best agreement with the neutron diffraction data is obtaine d with the parameters from the AUA4 (anisotropic united-atoms) force field recently proposed. (C) 2001 American Institute of Physics.