The structure of liquid carbon dioxide and carbon disulfide

Abstract

We present neutron and x-ray scattering data (a 2N+X experiment) of liquid CO(2) and CS(2) at a density of about 10 molecules/nm(3). Because the scattering length contrast of the carbon isotope is very small and, in fact, smaller than anticipated from standard scattering length tables, a direct partial structure factor determination via matrix inversion gives unconvincing results. Instead we search for the best representation of the three independent scattering data sets by a simulation of rigid molecules interacting via a 12-6-1 potential, furthermore restricting the pressure p, the density rho, and the temperature T to the experimental values. We show that a 12-6-1 potential is completely adequate to describe the structure of CO(2); for CS(2) we find that the best 12-6-1 potential still slightly overestimates the height of the sulfur-sulfur pair-distribution function g(SS). Orientational correlations reflect the similarities much more than the differences of the two molecular systems. The distinct differences in the atom-atom pair distribution functions of CO(2) and CS(2) do not mean that their structures are radically different and the comparison with the crystalline structures is somewhat deceptive. A linear transformation, wherein all the parameters describing the interaction and the geometry of CS(2) are changed to those of CO(2), allows us to point out the physical parameters which may be responsible for the differences or similarities in thermodynamic behavior (pressure) and structures (orientations) between the two liquids.

Molecular Simulation of CO2- and CO3-Brine-Mineral Systems

“…Some studies have been devoted to the properties of a single phase, such as the effect of density on the structure of scCO 2 along an isotherm (Ishii et al 1996), the structure of liquid CO 2 (Neuefeind et al 2009) or more rarely dynamical properties (In Het Panhuis et al, 1998;Nieto-Draghi et al 2007;Garcia-Ratés et al 2012). In all cases, comparison with experimental data provides a critical test of the accuracy of the force fields.…”

A first principles approach to the electronic properties of liquid and supercritical CO2

“…Recent researches also emphasize the interest in the combination of subcritical and supercritical CO 2 with ionic liquids 6 which may lead to the design of sophisticated multiphasic reaction environments. 6 Numerous investigations on the structure, [9][10][11][12][13][14][15][16][17][18][19] dynamics, 9,17 Raman spectrum, [20][21][22][23] and thermochemical properties 24-31 of CO 2 were reported. A very recent work discusses the absorption of CO 2 in a protic ionic liquid.…”

Structure of liquid carbon dioxide at pressures up to 10 GPa

“…The larger splitting between the two components is then easily explained by the longer length of the CS 2 molecule, and the larger probability to find molecules in the s-// configuration likely originates from the smaller quadrupole moment of CS 2 and thus weaker influence of the EQQ interactions in the intermolecular potential. As a matter of fact, the contribution of s-// molecules is readily apparent in the g CC (r) RDF of CS 2 at ambient pressure [27,49], unlike the low-density CO 2 fluid. The number of s-// molecules continuously grows in CS 2 up to 1.2 GPa, which is consistent with the general trend outlined above for quadrupolar liquids.…”

“…It is possible that a better match to the experimental data could be obtained by an ad-hoc fitting of the potential parameters [27] or by other methods, but we don't believe this would significantly change the conclusions drawn hereafter.…”

“…These studies have revealed that for states with liquidlike densities, the local order in the fluid is anisotropic, with significant orientational correlations between molecules due to the anisotropic character of the intermolecular interactions [23][24][25][26][27]. The question thus arises whether the local structure of the molecular liquid will be modified by the density increase, as observed in the solid phase.…”