Bond Angle Distributions of Carbon Dioxide in the Gas, Supercritical, and Solid Phases

Abstract

Recent work has focused attention on possible shifts in the bond angle distribution of CO(2) as a consequence of intermolecular interactions in the supercritical phase. To investigate the temperature and phase dependence of the intramolecular structure of CO(2), we performed Feynman path integral Monte Carlo calculations based on a spectroscopically derived analytical potential, first principles molecular dynamics simulations using Kohn-Sham density functional theory, and Monte Carlo simulations employing empirical interaction potentials. On the basis of various distributions used to characterize the intramolecular structure, we conclude that the aggregation state has a negligible influence on the intramolecular structure, in particular we find that in the classical limit the distributions are remarkably similar for the ideal gas, supercritical, and solid phases when considered at the same temperature. In contrast, an increase in the temperature from 325 to 673 K or inclusion of nuclear quantum effects leads to a significant broadening of the distributions. With respect to the first C-O bond vector, the second bond vector most prefers a collinear arrangement. However, due to the Jacobian factor the maximum in the bond angle distribution at 325 K is shifted to an angle of about 175.7 degrees in the classical limit or to 173.0 degrees if nuclear quantum effects are included. Nevertheless, an analysis of the temperature dependence of the constant-volume heat capacity demonstrates that carbon dioxide should be viewed as a linear molecule.

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

“…9,14,17 In particular, a comprehensive analysis of the bond angle distribution of CO 2 in the gas and condensed phases was reported by Anderson et al 14 It has been verified that an increase of the temperature from 375 to 673 K or the inclusion of quantum effects leads to a significant broadening of the distributions related to the CO bond distances. These authors also notice that CO 2 should not be viewed as a nonlinear molecule, although it could be represented by a flexible model with an equilibrium angle of 180 • .…”

“…These authors also notice that CO 2 should not be viewed as a nonlinear molecule, although it could be represented by a flexible model with an equilibrium angle of 180 • . 14 9 for scCO 2 at T = 318.15 K and ρ = 0.703 g cm −3 . In comparison with scCO 2 , N[cosθ] for liquid CO 2 shows a slightly faster decay to zero what reflects some smaller deviations from linearity of the CO 2 monomers.…”

“…13,14,17 The implications of these structural changes on the electronic properties of liquid and supercritical CO 2 deserve further attention. A recent work by Raveendran et al 44 discusses the polar attributes of scCO 2 .…”

“…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.…”

Solvation and Evolution Dynamics of an Excess Electron in SupercriticalCO2

“…Further, solvation in liquid or clusters or adsorption on solid surfaces could improve its EE-binding ability by stabilizing the EE-bound CO 2 motifs [32][33][34][35][36][37][38][39][40][41]. In particular, in the supercritical state, the CO 2 molecule is marginally nonlinear with an average angle of $174 , and thus possesses a small dipole moment [42][43][44][45][46][47]. Thus, scCO 2 could bind an EE through bending and solvation.…”