Ab initio studies on [bmim][PF6]-CO2 mixture and CO2 clusters

Abstract

Ab initio molecular dynamics studies have been carried out on the room temperature ionic liquid, 1,n-butyl,3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) and supercritical carbon dioxide mixture at room temperature and experimental density. Partial radial distribution functions (RDF) for different sites have been computed to see the organization of CO 2 molecules around the ionic liquid. Several partial RDFs around the carbon atom of CO 2 molecule are compared to find out that the CO 2 has specific interaction with a carbon atom present in the imidazolium ring. The CO 2 is also found to be very well organized around the terminal carbon atom of the butyl chain. The partial RDFs for the oxygen atoms around oxygen and carbon atoms of the CO 2 suggests that there is very good organization of CO 2 molecules around themselves even in the [bmim][PF 6 ] -CO 2 mixture. The instantaneous quadrupole moment tensor has been calculated for the anion and the cation. The ensemble average of diagonal components of quadrupole moment tensor of the cation have finite values, whereas the off-diagonal components of the cation and both the diagonal and off-diagonal components of the anion have the value of zero with a large standard deviation. The CPMD studies performed on CO 2 clusters reveals the greater tendency of the clusters with more CO 2 units, to deviate from the linear geometry.

Carbon capture with ionic liquids: overview and progress

“…54,[103][104][105][106][107][108] Up to now, most work has focused on [PF 6 ] and [Tf 2 N] anions, paired with imidazolium-based cations. 54,66,105,[109][110][111][112][113] For example, the reason for the partial molar volume of CO 2 being so small when dissolved in [bmim] [PF 6 ] was investigated by molecular dynamics simulations. It was found that most of the spaces occupied by CO 2 in the ionic liquids are larger cavities rather than those already existing in the pure ionic liquids.…”

Depolarization of water in protic ionic liquids

“…[83][84][85][86][87][88][89][90][91][92] Only a few AIMD studies of solute ILs mixtures were reported up to now. [93][94][95][96] In our investigation, we will study the influence of a small amount of water in mono-methylammonium nitrate (MMAN) on the IL and the change of the properties of water by this solvation. Previous studies of pure protic ammonium-based ILs and pure water have highlighted similar properties for both liquids.…”

Electronic absorption spectra and nonlinear optical properties of CO2 molecular aggregates: A quantum chemical study

“…CO 2 molecule in supercritical phase shows unique characteristics of liquid-like density and gas-like diffusivity in addition to its nontoxic behaviour, as observed in neutron diffraction experiments. [14][15][16] It has been observed in some earlier studies that, due to close proximity of the monomers in these dense phases, the CO 2 molecules no longer remain linear, [17][18][19][20] giving rise to instantaneous dipole moment. Thus we believe, which can be understood in the light of their linear and nonlinear optical response functions.…”

“…We have arranged several single molecular optimized structures in different special orientations and optimized further the molecular aggregates to obtain the cluster geometry, which can be seen possibly in dense CO 2 phases like supercritical one. [17][18][19] The calculated binding energies for these molecular assemblies are given in table 1. As can be seen, the dimer with slipped parallel geometry (D1) is slightly stabler than the T-shape one (D2).…”