Internal Pressure of Liquids and Solutions

Origin of parameter degeneracy and molecular shape relationships in geometric-flow calculations of solvation free energies

“…Table I also presents the errors RMSE exp for solvation free energy using experimental values for the pressure, p = 0.025 kcal mol −1 Å −3 , and surface tensio,n γ = 0.103 kcal mol −1 Å −2 , parameters. 10 For the pooled set, RMSE exp = 3.72RT which is very close to the global minimum error, RMSE min = 3.21RT at (p, γ ) = (0.045, 0.085). The difference between RMSE values is denoted by RMSE = RMSE exp − RMSE min ; the largest RMSE is 1.15 RT for the SAMPL0 set.…”

“…15,22,35 These observations, and our optimal surface tension and pressure estimates, are well explained by an internal pressure of p = 0.025 kcal mol −1 Å −3 but poorly explained by the use of atmospheric pressure. 10 In addition to statistical validation, we can demonstrate that these results are robust to the choice of force field used to model the small molecules. For the SAMPL0 set, we generate GAFF 30,31 parameters and compare the solvation free energy predictions from these parameters to those obtained from OPLS parameters.…”

“…10 Surface tension γ is characterized by the energy required to change the area of an interface and is often associated with the energetics of hydrogen bonding structure of water molecules near the solute/solvent interface. The experimental measurement for the water-air interface at 25…”

“…11 Because of water's high number and strength of hydrogen bonds, its surface tension is larger relative to its internal pressure than for organic liquids. 10 While models considering only the area of the cavity have been traditionally popular, 12,13 the recent inclusion of solute volume and nonpolar dispersive interactions in implicit solvation models is an important improvement. 3,4,6,14,15 Considerations from scaled particle theory 16,17 and multiple recent studies concerning the solute size-dependence of the hydrophobic effect [18][19][20] motivated this innovation which improves predictions of solvation forces and energies.…”

Acoustic Nonlinearity Parameter B/A, Internal Pressure, and Acoustic Impedance Determined at Pressures up to 100 MPa for 1-Ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide

“…The third goal is determination of the (p, T ) data of internal pressure which is closely related to the liquid structure, i.e. describes macroscopic effect of molecular interactions and plays an important role in the physical chemistry of the liquid state (Barton, 1971;Dack, 1975;Marcus, 2013). Investigations are completed by determination of the acoustic impedance Z in the given above (p, T ) range and all the present studies are based on the (p, T ) speed of sound data reported recently (Dzida et al, 2013).…”