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Optimization of linear and branched alkane interactions with water to simulate hydrophobic hydration
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10.1063/1.3623267
/content/aip/journal/jcp/135/5/10.1063/1.3623267
http://aip.metastore.ingenta.com/content/aip/journal/jcp/135/5/10.1063/1.3623267

Figures

Image of FIG. 1.
FIG. 1.

Hydration free energies of ethane, butane, and neopentane at atmospheric pressure as a function of temperature. For clarity, the hydration free energies of butane and neopentane are shifted up by 1 and 2 kcal/mol, respectively. The blue circles and red triangles correspond to simulation results using the TraPPE-UA and HH-Alkane models, respectively. Error bars indicate one standard deviation. The thin blue and red lines correspond to fits of Eq. (4c) to the TraPPE-UA and HH-Alkane simulation results, respectively. The thick black line indicates the experimental hydration free energies over the temperature range reported in Ref. 46.

Image of FIG. 2.
FIG. 2.

Parity plot comparing experimental and simulation alkane hydration free energies at atmospheric pressure. The blue circles and red triangles correspond to simulation results for the TraPPE-UA and HH-Alkane interaction potentials, respectively. Error bars indicate one standard deviation. The solid black line indicates exact agreement between experiment and simulations. The root mean square difference between experiment and the TraPPE-UA model predictions is 0.44 kcal/mol, while the root mean square difference for the HH-Alkane model predictions is 0.06 kcal/mol.

Image of FIG. 3.
FIG. 3.

Alkane carbon group/water oxygen radial distribution functions for propane and isobutane at 300 K. (a) The distribution functions for propane. The solid red line and red triangles indicate results for the terminal CH3 units of propane using the TraPPE-UA and HH-Alkane models, respectively. The dash blue line and blue circles indicate results for the middle CH2 unit of propane using the TraPPE-UA and HH-Alkane models, respectively. (b) The distribution functions for isobutane. The solid red line and red triangles indicate results for the pendant CH3 units of isobutane using the TraPPE-UA and HH-Alkane models, respectively. The dash blue line and blue circles indicate results for the central CH unit of isobutane using the TraPPE-UA and HH-Alkane models, respectively.

Tables

Generic image for table
Table I.

Cross alkane site/water oxygen Lennard-Jones interaction parameters for the TraPPE-UA and HH-Alkane models. TraPPE-UA/water cross interactions were determined using Lorentz-Berthelot combining rules (σiw = (σii + σww)/2 and εiw = (εiiεww)1/2) for the TIP4P/2005 water oxygen. The cross interaction thermal radius at 300 K was determined using Eq. (3).

Generic image for table
Table II.

Alkane hydration thermodynamic properties at 300 K and atmospheric pressure from experiment and simulation using the TraPPE-UA and HH-Alkane cross interaction models in TIP4P/2005 water. The experimental hydration thermodynamics were obtained from Ref. 46, except for those results marked by an “*” which were obtained from Ref. 47. The reported chemical potential, enthalpy, entropy, and heat capacity were obtained from fits of Eq. (4c) to the simulation free energies over the temperature range 270 K–370 K. The partial molar volumes were obtained by the difference method described in Sec. II. Errors in parentheses indicate one standard deviation.

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/content/aip/journal/jcp/135/5/10.1063/1.3623267
2011-08-03
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Optimization of linear and branched alkane interactions with water to simulate hydrophobic hydration
http://aip.metastore.ingenta.com/content/aip/journal/jcp/135/5/10.1063/1.3623267
10.1063/1.3623267
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