The dielectric constant: Reconciling simulation and experiment

Jorge, Miguel; Lue, Leo

doi:10.1063/1.5080927

Cited by 33 publications

(44 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For instance, the significant enhancement of the liquid dipole moment supports previous assertions by ourselves [11,13,124] and others [8,10,43,123] that classical fixed-charge models should not be expected to yield accurate predictions of the static dielectric constant of water, which depends on the dipole moment surface of the system. Instead, one needs to apply a correction for the fact that the dipole moment of fixed-charge models (normally between 2.2 and 2.4 D) is actually an effective value that is scaled down with respect to the real liquid phase dipole moment (of around 2.8 to 3.0 D) [8,10,11,44]. This also means that point charges obtained from SCEE (or any other QMbased approach to describe the liquid state) should not be used directly in fixed-charge force fields.…”

Section: Discussionsupporting

confidence: 77%

“…where E  ∞ was obtained from the first step of a single-point SCRF calculation starting from the polarized QM wave function surrounded by a continuum with dielectric constant equal to the high-frequency dielectric constant of water. For these single-point energy calculations, we used the SCIPCM model [109], as implemented in Gaussian 09, with a value of ∞ = 1.766, determined from the square of the experimental index of refraction at the Sodium D-line frequency [11]. This energy term describes in an approximate way the interaction between the polarized wave function and the electronic degrees of freedom of the surrounding liquid [8].…”

Section: Self-consistent Electrostatic Embedding Approachmentioning

confidence: 99%

“…Moreover, and of particular interest from the point of view of force-field development, knowledge of the liquidphase dipole moment can be used to derive polarization corrections for phase-change properties, e.g. the enthalpy of vaporization and the solvation free energy [8,9], and for electronic properties such as the dielectric constant [10,11]. It can also inform the assignment of point charges to non-polarizable models so as to approximately capture the potential energy surface (PES) of a polarized liquid phase [12].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Self-consistent electrostatic embedding for liquid phase polarization

Jorge

Gomes

Milne

2021

Journal of Molecular Liquids

Self Cite

View full text Add to dashboard Cite

While it is well known that molecules can be strongly polarized when transferred from the gas phase to a polar liquid, quantifying polarization effects explicitly using either experiment or theory has remained elusive. In this paper, we present a new QM/MM method involving a selfconsistent calculation of the liquid state dipole moments, that is able to yield realistic, accurate estimates of the multipole moments of molecules in the liquid state. As a proof-of-concept, we apply our Self-Consistent Electrostatic Embedding (SCEE) method to the widely studied system of pure water. The method gives molecular dipole moments that are significantly enhanced with respect to the isolated gas-phase molecule and that are consistent with the best current experimental estimate of this property. While previous QM/MM calculations on the same system systematically underestimate the liquid dipole moment, those predictions become consistent with our own when several shortcomings are accounted for in an approximate way.Furthermore, sampling liquid configurations using several (but not all) fixed-charge force fields yields results that are consistent with sampling from a classical polarizable model. We then extract several contributions to the polarization energy (i.e. the change in energy when transferring a molecule from the gas to the liquid phase) and show that the distortion correction is cancelled out by the purely electronic contribution to the polarization energy. This insight is very important from the point of view of force-field development, since it allows us to unequivocally quantify the two missing energy terms in classical non-polarizable models. This provides a way to systematically improve predictions of phase-change energies (e.g. enthalpy of vaporization, hydration free energies) from such force-fields by correcting for the missing polarization effects.

show abstract

Section: Discussionsupporting

confidence: 77%

Section: Self-consistent Electrostatic Embedding Approachmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Self-consistent electrostatic embedding for liquid phase polarization

Jorge

Gomes

Milne

2021

Journal of Molecular Liquids

Self Cite

View full text Add to dashboard Cite

show abstract

“…The idea of using scaled charges for ions in water is usually denoted as the electronic continuum correction (ECC). It can also be regarded as a consequence of the fact that the potential energy and the dipole moment surfaces may need different parameters to be described by empirical force fields [78,79]. Soon other groups, as that of Jungwirth [58,80,81], Barbosa [82], and Wang [83,84] adopted this idea.…”

Section: Introductionmentioning

confidence: 99%

Scaled charges at work: Salting out and interfacial tension of methane with electrolyte solutions from computer simulations

Blazquez

Zerón

Conde

et al. 2020

Fluid Phase Equilibria

View full text Add to dashboard Cite

The solubility of methane in water decreases when a small amount of salt is present. This is usually denoted as the salting out effect (i.e., the methane is expelled from the solution when it contains small amounts of salt). The effect is important, for instance the solubility is reduced by a factor of three in a 4 m (mol/kg) NaCl solution. Some years ago we showed that the salting out effect of methane in water can be described qualitatively by molecular models using computer simulations. However the salting out effect was overestimated. In fact, it was found that the solubility of methane was reduced by a factor of eight. This points to limitations in the force field used. In this work we have carried out direct coexistence simulations to describe the salting out effect of methane in water using a recently proposed force field (denoted as Madrid-2019) based on the use of scaled charges for the ions and the TIP4P/2005 force field for water. For NaCl the results of the Madrid-2019 force field significantly improve the description of salting out of methane. For other salts the results are quite reasonable. Thus the reduction of the charge of the ions also seems to be able to improve the description of salting out effect of methane in water. Besides this we shall show that the brine-methane interface exhibits an increased interfacial tension as compared to that of the water-methane system. It is well known that electrolytes tend to increase the surface tension of liquid water, and this seems also to be the case for the interface between water and methane.

show abstract

“…In fact, as argued by Leontyev and Stuchebrukhov [24][25][26] the force field charges (and hence the dipole moment of the molecular model) can be interpreted as effective scaled charges, that are adjusted down from the charges that would represent the real liquid dipole moment. This is one of the reasons why most fixed-charge force fields have dipole moments that are approximately half-way between the gas and the liquid dipole moments [27][28][29][30] A direct consequence of this choice is that fixed-charge force fields are then unable to accurately predict properties that depend directly on the dipole moment surface (DMS), such as the dielectric constant 23,30,31 .…”

Section: Introductionmentioning

confidence: 99%