A Kirkwood−Buff Derived Force Field for Methanol and Aqueous Methanol Solutions

Weerasinghe, Samantha; Smith, Paul E.

doi:10.1021/jp051773i

Cited by 110 publications

(216 citation statements)

References 73 publications

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“…(4) in theory but it is typically statistically unreliable. 81 Instead it was calculated from 30, 82…”

Section: Methodsmentioning

confidence: 99%

“…This has been observed in other types of aqueous solutions as well. 81 The phenomenon is essentially a natural consequence of crowding as well as the normalization of the RDFs to unity at infinite separation. As the number of solute molecules increases the number of solute molecules with which to interact increases leading to increases in g cc .…”

Section: Kirkwood-buff Solution Analysismentioning

confidence: 99%

“…(1) by integrating the RDFs via the trapezoidal rule and taking the average between 10 and 15 Å. 81 Previous KB studies used averages from 9.5 to 12 Å 81 or from 15 to 20 Å. 81,92 As shown in Fig.…”

Section: Kirkwood-buff Solution Analysismentioning

confidence: 99%

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Kirkwood-Buff analysis of aqueous N-methylacetamide and acetamide solutions modeled by the CHARMM additive and Drude polarizable force fields

Lin

Lopes

Roux

et al. 2013

The Journal of Chemical Physics

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Kirkwood-Buff analysis was performed on aqueous solutions of N-methylacetamide and acetamide using the Chemistry at HARvard Molecular Mechanics additive and Drude polarizable all-atom force fields. Comparison of a range of properties with experimental results, including Kirkwood-Buff integrals, excess coordination numbers, solution densities, partial molar values, molar enthalpy of mixing, showed both models to be well behaved at higher solute concentrations with the Drude model showing systematic improvement at lower solution concentrations. However, both models showed difficulties reproducing experimental activity derivatives and the excess Gibbs energy, with the Drude model performing slightly better. At the molecular level, the improved agreement of the Drude model at low solute concentrations is due to increased structure in the solute-solute and solute-solvent interactions. The present results indicate that the explicit inclusion of electronic polarization leads to improved modeling of dilute solutions even when those properties are not included as target data during force field optimization.

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“…(4) in theory but it is typically statistically unreliable. 81 Instead it was calculated from 30, 82…”

Section: Methodsmentioning

confidence: 99%

Section: Kirkwood-buff Solution Analysismentioning

confidence: 99%

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Kirkwood-Buff analysis of aqueous N-methylacetamide and acetamide solutions modeled by the CHARMM additive and Drude polarizable force fields

Lin

Lopes

Roux

et al. 2013

The Journal of Chemical Physics

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“…Despite this shortcoming, it turns out that both type of quantities coherently point to the same microstructure of neat alcohol. Two models of MetOH are studied, the OPLS model [15] and the more recent WS model [6], and for TBA the OPLS model [15]. Both MetOH models have 3 sites, one for O, H, and one for the methyl group M = CH 3 .…”

mentioning

confidence: 99%

Microstructure of neat alcohols

2007

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Formation of microstructure in homogeneous associated liquids is analysed through the densitydensity pair correlation functions, both in direct and reciprocal space, as well as an effective local one-body density function. This is illustrated through a molecular dynamics study of two neat alcohols, namely methanol and tert-butanol, which have a rich microstructure: chain-like molecular association for the former and micelle-like for the latter. The relation to hydrogen bonding interaction is demonstrated. The apparent failure to find microstructure in water -a stronger hydrogen bonding liquid-with the same tools, is discussed.Liquids are generally thought as macroscopically homogeneous when they are considered far from phase transitions and interfacial regions. From a statistical mechanical point of view, homogeneity is expressed by the fact that the order parameter, in this case the one body density, which formally depends on both the position and orientation of a single particle 1 (as in a crystal or a liquid crystal, for example), is a constant throughout the sample: ρ (1) (1) = ρ = N/V , where N is the number of particles per volume V. As a consequence, the microscopic description of the structure of a neat liquid starts from the two-body density function ρ (2) (1, 2) = ρ (1) (1)ρ (1) (2)g(1, 2) that expresses the density correlations between particles 1 and 2, and reduces in this case to ρ 2 g(1, 2) , where g(1, 2) is the pair distribution function. Associated liquids, such as water and alcohols, for example, belong to a special class because of the particularity of the hydrogen bonding (HB) that is highly directional, and tend to enhance the structure the liquid locally. One particularly interesting example of this phenomena is the microheterogeneous nature of aqueous mixtures, which has attracted a recent upsurge of interest [1,2,3,4,5,6,7]. Perhaps the most remarkable reported fact is that watermethanol mixtures show local immiscibility at microscopic level, while being miscible at macroscopic level [1,2]. In order to appreciate this result it is interesting to compare it to microemulsions where bicontinuous phases are usually observed, and micro-immiscibility operates with domain sizes ranging from 100 nanometers to few micrometers, while those mentioned here are around few nanometers-that is about few molecular diameters. In addition, it is important to note that bicontinuous phases in microemulsions arise after a phase transition has occurred from disordered to ordered phase; while in the former case, we are still in a genuinely homogeneous and disordered liquid phase. From these facts, microheterogeneity in aqueous mixtures can be considered as both obvious and mysterious, obvious because the mechanism behind it is the strong directionality of the hydrogen bonding, and mysterious because of the existence of stable microimmiscibility of water and solute in a macroscopically homogeneous sample. In contrast to the situation for mixtures, neat water do not seem to exhibit any micro phase separation betwe...

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“…4 The integrals have been extensively used in the development of accurate force fields for fluid mixtures. [5][6][7][8][9][10][11][12] Christensen et al 4,13,14 utilized the integrals in a methodology for predicting the excess Gibbs energy of liquid mixtures. They simulated the mixture at a few compositions using molecular dynamics and then regressed parameters of the modified Margules G E model.…”

Section: Introductionmentioning

confidence: 99%

Pair correlation function integrals: Computation and use

Wedberg

O’Connell

Peters

et al. 2011

The Journal of Chemical Physics

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We describe a method for extending radial distribution functions obtained from molecular simulations of pure and mixed molecular fluids to arbitrary distances. The method allows total correlation function integrals to be reliably calculated from simulations of relatively small systems. The long-distance behavior of radial distribution functions is determined by requiring that the corresponding direct correlation functions follow certain approximations at long distances. We have briefly described the method and tested its performance in previous communications [R. Wedberg, J. P. O'Connell, G. H. Peters, and J. Abildskov, Mol. Simul. 36, 1243 (2010); Fluid Phase Equilib. 302, 32 (2011)], but describe here its theoretical basis more thoroughly and derive long-distance approximations for the direct correlation functions. We describe the numerical implementation of the method in detail, and report numerical tests complementing previous results. Pure molecular fluids are here studied in the isothermal-isobaric ensemble with isothermal compressibilities evaluated from the total correlation function integrals and compared with values derived from volume fluctuations. For systems where the radial distribution function has structure beyond the sampling limit imposed by the system size, the integration is more reliable, and usually more accurate, than simple integral truncation.

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A Kirkwood−Buff Derived Force Field for Methanol and Aqueous Methanol Solutions

Cited by 110 publications

References 73 publications

Kirkwood-Buff analysis of aqueous N-methylacetamide and acetamide solutions modeled by the CHARMM additive and Drude polarizable force fields

Kirkwood-Buff analysis of aqueous N-methylacetamide and acetamide solutions modeled by the CHARMM additive and Drude polarizable force fields

Microstructure of neat alcohols

Pair correlation function integrals: Computation and use

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