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Optimizing potentials for a liquid mixture: a new force field for a tert-butanol and water solution.

Di Pierro M, Mugnai ML, Elber R - J Phys Chem B (2014)

Bottom Line: We apply the newly developed technology to study the liquid mixture of tert-butanol and water.We are able to obtain, after four iterations, the correct phase behavior and accurately predict the value of the Kirkwood Buff (KB) integrals.We further illustrate that a potential that is determined solely by KB information, or the pair correlation function, is not necessarily unique.

View Article: PubMed Central - PubMed

Affiliation: Institute for Computational Engineering and Sciences and ‡Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States.

ABSTRACT
A technology for optimization of potential parameters from condensed-phase simulations (POP) is discussed and illustrated. It is based on direct calculations of the derivatives of macroscopic observables with respect to the potential parameters. The derivatives are used in a local minimization scheme, comparing simulated and experimental data. In particular, we show that the Newton trust region protocol allows for more accurate and robust optimization. We apply the newly developed technology to study the liquid mixture of tert-butanol and water. We are able to obtain, after four iterations, the correct phase behavior and accurately predict the value of the Kirkwood Buff (KB) integrals. We further illustrate that a potential that is determined solely by KB information, or the pair correlation function, is not necessarily unique.

No MeSH data available.


Related in: MedlinePlus

KB integralsas a function of TBA mole fraction. (A) TBA–TBA; (B) TBA–water;(C) water–water. The blue line shows the experimental resultsfrom ref (19), thered line shows results from Lee and Van Der Vegt potential,15 the green line shows computational results fromforce field POP3ff, and the purple line shows computational resultsfrom force field POP4ff.
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fig5: KB integralsas a function of TBA mole fraction. (A) TBA–TBA; (B) TBA–water;(C) water–water. The blue line shows the experimental resultsfrom ref (19), thered line shows results from Lee and Van Der Vegt potential,15 the green line shows computational results fromforce field POP3ff, and the purple line shows computational resultsfrom force field POP4ff.

Mentions: After the third iteration, the optimization procedure producedonly minor improvements. We therefore decided to use a more informativetarget function. Inspection of the results over a broader range ofconcentrations suggested using as targets the KB integrals at TBAmole fractions of 0.04 and 0.10. The experimental KB integral of speciesTBA–TBA exhibits a global minimum at a TBA mole fraction of0.04 and a global maximum at a TBA mole fraction of 0.10 (see squaresin Figure 5). This feature is missing in theforce field obtained after the third iteration (Figure 5). Iteration IV produced a significantimprovement over the whole concentration range. The force field producedby the fourth iteration (POP4ff) reproduces very well the three KBintegrals over a wide concentration range (0.04–0.3), outperformingboth OPLSUA and the force field developed by Lee and Van Der Vegt.The KB integrals for the different force fields as functions of theconcentration are shown in Figure 5. Note thatonly TBA mole fractions of 0.2, 0.04, and 0.1 were used at any timein the optimization, leaving us ample data for meaningful testing.


Optimizing potentials for a liquid mixture: a new force field for a tert-butanol and water solution.

Di Pierro M, Mugnai ML, Elber R - J Phys Chem B (2014)

KB integralsas a function of TBA mole fraction. (A) TBA–TBA; (B) TBA–water;(C) water–water. The blue line shows the experimental resultsfrom ref (19), thered line shows results from Lee and Van Der Vegt potential,15 the green line shows computational results fromforce field POP3ff, and the purple line shows computational resultsfrom force field POP4ff.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4306501&req=5

fig5: KB integralsas a function of TBA mole fraction. (A) TBA–TBA; (B) TBA–water;(C) water–water. The blue line shows the experimental resultsfrom ref (19), thered line shows results from Lee and Van Der Vegt potential,15 the green line shows computational results fromforce field POP3ff, and the purple line shows computational resultsfrom force field POP4ff.
Mentions: After the third iteration, the optimization procedure producedonly minor improvements. We therefore decided to use a more informativetarget function. Inspection of the results over a broader range ofconcentrations suggested using as targets the KB integrals at TBAmole fractions of 0.04 and 0.10. The experimental KB integral of speciesTBA–TBA exhibits a global minimum at a TBA mole fraction of0.04 and a global maximum at a TBA mole fraction of 0.10 (see squaresin Figure 5). This feature is missing in theforce field obtained after the third iteration (Figure 5). Iteration IV produced a significantimprovement over the whole concentration range. The force field producedby the fourth iteration (POP4ff) reproduces very well the three KBintegrals over a wide concentration range (0.04–0.3), outperformingboth OPLSUA and the force field developed by Lee and Van Der Vegt.The KB integrals for the different force fields as functions of theconcentration are shown in Figure 5. Note thatonly TBA mole fractions of 0.2, 0.04, and 0.1 were used at any timein the optimization, leaving us ample data for meaningful testing.

Bottom Line: We apply the newly developed technology to study the liquid mixture of tert-butanol and water.We are able to obtain, after four iterations, the correct phase behavior and accurately predict the value of the Kirkwood Buff (KB) integrals.We further illustrate that a potential that is determined solely by KB information, or the pair correlation function, is not necessarily unique.

View Article: PubMed Central - PubMed

Affiliation: Institute for Computational Engineering and Sciences and ‡Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States.

ABSTRACT
A technology for optimization of potential parameters from condensed-phase simulations (POP) is discussed and illustrated. It is based on direct calculations of the derivatives of macroscopic observables with respect to the potential parameters. The derivatives are used in a local minimization scheme, comparing simulated and experimental data. In particular, we show that the Newton trust region protocol allows for more accurate and robust optimization. We apply the newly developed technology to study the liquid mixture of tert-butanol and water. We are able to obtain, after four iterations, the correct phase behavior and accurately predict the value of the Kirkwood Buff (KB) integrals. We further illustrate that a potential that is determined solely by KB information, or the pair correlation function, is not necessarily unique.

No MeSH data available.


Related in: MedlinePlus