Orientational correlations in liquid and supercritical CO2: neutron diffraction experiments and molecular dynamics simulations

Neutron diffraction data from sub- and supercritical CO2, collected over th ree different experimental runs, are analysed together, in order to investi gate the evolution of the microscopic structure with the thermodynamic para meters. The relative orientations of neighbouring molecules are analysed al so in terms of the angular radial correlation function, obtained by molecul ar dynamics simulation runs compatible with the total neutron weight ed rad ial distribution function. Orientational correlations between neighbouring molecules are seen to persist across the whole thermodynamic range investig ated. However, these are limited to the first neighbouring shell, and mainl y ascribable to the quadrupolar interaction.