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CO2 solvation free energy using quasi-chemical theory
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10.1063/1.3598470
/content/aip/journal/jcp/134/22/10.1063/1.3598470
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/22/10.1063/1.3598470

Figures

Image of FIG. 1.
FIG. 1.

The simulation box with CO2 solvated in water. CO2 is displayed in ball-and-stick form while water molecules are shown in licorice representation. The three overlapping spherical volumes represent the inner-shell region with Ro = 3.3 Å (radius of the sphere centered on oxygen atoms) and Rc = 3.925 Å (radius of the sphere centered on the carbon atom).

Image of FIG. 2.
FIG. 2.

Radial distribution function (RDF), g(r), of CO2 and water oxygen atoms. Blue line depicts the RDF of CO2 carbon and water oxygens. Green and red lines represent the RDFs of two CO2 oxygens and water oxygens. The shoulder of the CO2 carbon-water RDF is presumably due to the uneven distribution of the water molecules in the first hydration shell caused by the existence of the two CO2 oxygens.

Image of FIG. 3.
FIG. 3.

Inner-shell free energy contribution based on corrdination number distribution (RT lnxn) with the inner-shell boundary at Rc = 3.925 Å (Ro = 3.3 Å). The red line with squares gives the observed data points while the black line is the extra/interpolation of a second-order polynomial function.

Image of FIG. 4.
FIG. 4.

Packing contribution to the solvation free energy in terms of radius. Red squares are the observed points. The solid black line represents the extrapolation of a polynomial function.

Image of FIG. 5.
FIG. 5.

Decomposition of solvation free energy of CO2 with respect to the radius of the inner shell. Blue diamonds represent the inner-shell chemical contribution; red squares represent the packing term; green triangles are the long-range contributions including electrostatics and van der Waals terms. The sum gives the total solvation free energy, denoted in purple crosses.

Image of FIG. 6.
FIG. 6.

Coordination number distributions, p(n), for various inner-shell radii ranging from 2.7 to 3.3 Å. The most probable number of water molecules surrounding CO2 in liquid water ranges from n = 1 to n = 7, depending on the inner-shell observation volume.

Image of FIG. 7.
FIG. 7.

QM-optimized structures of CO2-water clusters with various numbers of water ligands from n = 1 to n = 6.

Tables

Generic image for table
Table I.

Van der Waals parameters for CO2 and water interactions. The parameters were determined using the combination rule (Ref. 41) from the AMBER force field. ε ij is the well depth of the potential while σ ij is the radius. Ow represents the oxygen atom of water.

Generic image for table
Table II.

Hydration free energies of CO2 in terms of coordination number using the cluster approach. Individual terms are listed. μ IS , the total inner-shell contribution, includes the gas-phase binding free energy ΔG (0), anharmonicity correction G anharm, inner-shell dispersion effects, , the density term μ den = nRTln1354, the entropic penalty and the probability term RTlnp(n). The outer-shell components consist of the long-range electrostatic interaction, ; long-range van der Waals interaction, ; and molecular packing term, Δμ pac . μ ex is the total solvation free energy.

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/content/aip/journal/jcp/134/22/10.1063/1.3598470
2011-06-14
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: CO2 solvation free energy using quasi-chemical theory
http://aip.metastore.ingenta.com/content/aip/journal/jcp/134/22/10.1063/1.3598470
10.1063/1.3598470
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