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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: In particular, we show that the Newton trust region protocol allows for more accurate and robust optimization.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

(A) Paircorrelation function for species TBA–TBA; the yellow curveis the pair correlation function computed with the OPLS force field,the green curve is the pair correlation function computed with POP3ff,and the purple curve is the pair correlation function computed withforce field POP4ff. (B,C) The same information as (A) for speciesTBA–water and water–water. All of the results were obtainedat a TBA mole fraction of 0.20.
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fig6: (A) Paircorrelation function for species TBA–TBA; the yellow curveis the pair correlation function computed with the OPLS force field,the green curve is the pair correlation function computed with POP3ff,and the purple curve is the pair correlation function computed withforce field POP4ff. (B,C) The same information as (A) for speciesTBA–water and water–water. All of the results were obtainedat a TBA mole fraction of 0.20.

Mentions: The pair correlation functions of TBA-TBA, TBA–waterand water–water are shown in Figure 6. It is clear that the system is now well mixed because long-rangecorrelations are absent. The pair correlation functions of TBA–TBAand TBA–water of OPLSUA (yellow in Figure 6) and POP4ff (purple in Figure 6) are significantlydifferent; OPLSUA shows two nearby peaks, whereas POP4ff shows a singlesmooth peak. The pair correlation functions of force fields POP3ff(green in Figure 6) and POP4ff deviate onlyslightly. We did not include any information about the shape of thepair correlation functions in the target function; this change isa byproduct of the optimization procedure. Whether this is corrector not is difficult to say because we do not know the pair correlationfunction from experiment, only its integral, which hides such features.


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)

(A) Paircorrelation function for species TBA–TBA; the yellow curveis the pair correlation function computed with the OPLS force field,the green curve is the pair correlation function computed with POP3ff,and the purple curve is the pair correlation function computed withforce field POP4ff. (B,C) The same information as (A) for speciesTBA–water and water–water. All of the results were obtainedat a TBA mole fraction of 0.20.
© Copyright Policy
Related In: Results  -  Collection

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

fig6: (A) Paircorrelation function for species TBA–TBA; the yellow curveis the pair correlation function computed with the OPLS force field,the green curve is the pair correlation function computed with POP3ff,and the purple curve is the pair correlation function computed withforce field POP4ff. (B,C) The same information as (A) for speciesTBA–water and water–water. All of the results were obtainedat a TBA mole fraction of 0.20.
Mentions: The pair correlation functions of TBA-TBA, TBA–waterand water–water are shown in Figure 6. It is clear that the system is now well mixed because long-rangecorrelations are absent. The pair correlation functions of TBA–TBAand TBA–water of OPLSUA (yellow in Figure 6) and POP4ff (purple in Figure 6) are significantlydifferent; OPLSUA shows two nearby peaks, whereas POP4ff shows a singlesmooth peak. The pair correlation functions of force fields POP3ff(green in Figure 6) and POP4ff deviate onlyslightly. We did not include any information about the shape of thepair correlation functions in the target function; this change isa byproduct of the optimization procedure. Whether this is corrector not is difficult to say because we do not know the pair correlationfunction from experiment, only its integral, which hides such features.

Bottom Line: In particular, we show that the Newton trust region protocol allows for more accurate and robust optimization.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