LOCAL ORIENTATIONAL CORRELATIONS IN FLUID CO2 IN A WIDE-RANGE OF THERMODYNAMIC PARAMETERS

In this paper we present a thorough study of the local microscopic str ucture of carbon dioxide in a wide thermodynamic region, coveting both undercritical and supercritical states. From neutron diffraction meas urements we derive accurate information an the neutron weighted distri bution function, g(nw) (r), which allows us to single out a realistic interaction potential to be used in Molecular Dynamics (MD) simulation s. These MD simulations are then performed to supplement the informati on obtained from the neutron scattering experiments. In such a way we determine appropriate averages of the molecular distribution function, g(R, omega(1),omega(2)). The presence of preferred relative orientati ons between neighbouring molecules is evident. We find that, among fir st neighbouring molecules, T-shaped configurations are largely preferr ed in all the investigated thermodynamic states and that electrostatic interactions play a crucial role in determining the local structure o f the fluid.