Local orientational correlations in fluidCO ₂ in a wide range of thermodynamic parameters

Summary

In this paper we present a thorough study of the local microscopic structure of carbon dioxide in a wide thermodynamic region, covering both undercritical and supercritical states. From neutron diffraction measurements we derive accurate information on the neutron weighted distribution function,g _nw (τ), which allows us to single out a realistic interaction potential to be used in Molecular Dynamics (MD) simulations. These MD simulations are then performed to supplement the information obtained from the neutron scattering experiments. In such a way we determine appropriateaverages of the molecular distribution function,g(R, ω₁,ω₂). The presence of preferred relative orientations between neighbouring molecules is evident. We find that, among first neighbouring molecules,T-shaped configurations are largely preferred in all the investigated thermodynamic states and that electrostatic interactions play a crucial role in determining the local structure of the fluid.