Comparison of selected site–site RDFs between the neat OPLS (thicker lines) and TraPPE-UA (thinner line) models. Top panel for oxygen–oxygen, middle panel for carbon–carbon, and bottom for methyl–methyl site–site RDFs.
Enthalpies (top panel) and volumes (lower panel) for the aqueous TBA mixtures as function of the TBA mole fraction. Insets: corresponding excess quantities. Red lines for expt. data, enthalpies from Ref. 50 and volumes from Ref. 51 , green dots are simulation results from Ref. 17 , blue dots for OPLS TBA and purple dots for TraPPE-UA TBA. Lines connecting the dots are guidelines.
(a) Snapshots for the OPLS TBA aqueous mixtures for three different TBA mole fractions. Water molecules are shown as red spheres for oxygen and white spheres for hydrogen. TBA is shown as semi-transparent molecule, with cyan sphere for oxygen and white spheres for hydrogen. (b) Snapshots for the TraPPE-UA TBA aqueous mixtures for three different TBA mole fractions. The conventions are as in (a).
Corrected KBI (symbols) from various TBA models versus TBA mole fraction x, compared to various experimental ones: continuous lines from Ref. 44 , dashed lines from Ref. 45 , magneta lines for SAXS data from Ref. 30 and cyan lines for SANS data from Ref. 44 . Present calculations are shown in filled dots for the OPLS model and squares for the TraPPE-UA model. The color conventions are blue for G WW , red for G AA , and green for G WA . Note that the SAXS and SANS data are undifferentiated (see text for more details).
Details of TS extension procedure for the OPLS TBA oxygen–oxygen correlations for the TBA mole fraction x = 0.2. Top panel, tail part of (the short range part shown in the inset): red dashed line for the uncorrected data, blue line after TS correction. Middle panel, RKBI with same line conventions as in top panel. Lower panel, structure factor with same line conventions as in top panel. The green curve is the structure factor of neat TBA.
Same as Fig. 6 but for water oxygen–oxygen correlations for x = 0.2. The gold curve in the inset of the lower panel is the structure factor of neat water.
Same as Fig. 6 but for x = 0.8. The green slanted line in the middle panel shows the wrong slope of the uncorrected data before the LP correction (see text). The green curve in the lower panel is the structure factor of neat TBA.
Selected site–site RDFs for x = 0.5. Top panel: TBA–TBA correlations through carbon–carbong CC (r). Middle panel water-TBC cross correlations through TBA oxygen and water hydrogen g OH (r). Lower panel water–water correlations through oxygen–oxygen g OO (r). Red for the OPLS, blue for the TraPPE-UA mixture models of present work, and green for the mixture model of Ref. 17 .
Comparison between the force field parameters for TBA.
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