Nuclear Quantum Effects on Autoionization of Water Isotopologues Studied by Ab Initio Path Integral Molecular Dynamics
| Title: | Nuclear Quantum Effects on Autoionization of Water Isotopologues Studied by Ab Initio Path Integral Molecular Dynamics |
|---|---|
| Authors: | Thomsen, Bo, Shiga, Motoyuki |
| Publication Year: | 2021 |
| Collection: | Condensed Matter Physics (Other) |
| Subject Terms: | Physics - Chemical Physics, Condensed Matter - Materials Science, Physics - Computational Physics |
| More Details: | In this study we investigate the nuclear quantum effects (NQEs) on the acidity constant (pKA) of liquid water isotopologues at the ambient condition by path integral molecular dynamics (PIMD) simulations. We compared simulations using a fully explicit solvent model with a classical polarizable force field, density functional tight binding, and ab initio density functional theory, which correspond to empirical, semiempirical, and ab initio PIMD simulations, respectively. The centroid variable with respect to the proton coordination number of a water molecule was restrained to compute the gradient of the free energy, which measures the reversible work of the proton abstraction for the quantum mechanical system. The free energy curve obtained by thermodynamic integration was used to compute the pKA value based on probabilistic determination. This technique not only reproduces the pKA value of liquid D2O experimentally measured (14.86) but also allows for a theoretical prediction of the pKA values of liquid T2O, aqueous HDO and HTO which are unknown due to its scarcity. It is also shown that the NQEs on the free energy curve can result in a downshift of 4.5 +/- 0.9 pKA units in the case of liquid water, which indicates that the NQEs plays an indispensable role in the absolute determination of pKA. The results of this study can help to inform further extensions into the calculation of the acidity constants of isotope substituted species with high accuracy. Comment: The following article has been accepted by Journal of Chemical Physics. After it is published, it will be found at Link https://aip.scitation.org/journal/jcp. Copyright (2021) Bo Thomsen and Motoyuki Shiga. This article is distributed under a Creative Commons Attribution (CC BY) License |
| Document Type: | Working Paper |
| DOI: | 10.1063/5.0040791 |
| Access URL: | http://arxiv.org/abs/2101.12500 |
| Accession Number: | edsarx.2101.12500 |
| Database: | arXiv |
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| Items | – Name: Title Label: Title Group: Ti Data: Nuclear Quantum Effects on Autoionization of Water Isotopologues Studied by Ab Initio Path Integral Molecular Dynamics – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Thomsen%2C+Bo%22">Thomsen, Bo</searchLink><br /><searchLink fieldCode="AR" term="%22Shiga%2C+Motoyuki%22">Shiga, Motoyuki</searchLink> – Name: DatePubCY Label: Publication Year Group: Date Data: 2021 – Name: Subset Label: Collection Group: HoldingsInfo Data: Condensed Matter<br />Physics (Other) – Name: Subject Label: Subject Terms Group: Su Data: <searchLink fieldCode="DE" term="%22Physics+-+Chemical+Physics%22">Physics - Chemical Physics</searchLink><br /><searchLink fieldCode="DE" term="%22Condensed+Matter+-+Materials+Science%22">Condensed Matter - Materials Science</searchLink><br /><searchLink fieldCode="DE" term="%22Physics+-+Computational+Physics%22">Physics - Computational Physics</searchLink> – Name: Abstract Label: Description Group: Ab Data: In this study we investigate the nuclear quantum effects (NQEs) on the acidity constant (pKA) of liquid water isotopologues at the ambient condition by path integral molecular dynamics (PIMD) simulations. We compared simulations using a fully explicit solvent model with a classical polarizable force field, density functional tight binding, and ab initio density functional theory, which correspond to empirical, semiempirical, and ab initio PIMD simulations, respectively. The centroid variable with respect to the proton coordination number of a water molecule was restrained to compute the gradient of the free energy, which measures the reversible work of the proton abstraction for the quantum mechanical system. The free energy curve obtained by thermodynamic integration was used to compute the pKA value based on probabilistic determination. This technique not only reproduces the pKA value of liquid D2O experimentally measured (14.86) but also allows for a theoretical prediction of the pKA values of liquid T2O, aqueous HDO and HTO which are unknown due to its scarcity. It is also shown that the NQEs on the free energy curve can result in a downshift of 4.5 +/- 0.9 pKA units in the case of liquid water, which indicates that the NQEs plays an indispensable role in the absolute determination of pKA. The results of this study can help to inform further extensions into the calculation of the acidity constants of isotope substituted species with high accuracy.<br />Comment: The following article has been accepted by Journal of Chemical Physics. After it is published, it will be found at Link https://aip.scitation.org/journal/jcp. Copyright (2021) Bo Thomsen and Motoyuki Shiga. This article is distributed under a Creative Commons Attribution (CC BY) License – Name: TypeDocument Label: Document Type Group: TypDoc Data: Working Paper – Name: DOI Label: DOI Group: ID Data: 10.1063/5.0040791 – Name: URL Label: Access URL Group: URL Data: <link linkTarget="URL" linkTerm="http://arxiv.org/abs/2101.12500" linkWindow="_blank">http://arxiv.org/abs/2101.12500</link> – Name: AN Label: Accession Number Group: ID Data: edsarx.2101.12500 |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1063/5.0040791 Subjects: – SubjectFull: Physics - Chemical Physics Type: general – SubjectFull: Condensed Matter - Materials Science Type: general – SubjectFull: Physics - Computational Physics Type: general Titles: – TitleFull: Nuclear Quantum Effects on Autoionization of Water Isotopologues Studied by Ab Initio Path Integral Molecular Dynamics Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Thomsen, Bo – PersonEntity: Name: NameFull: Shiga, Motoyuki IsPartOfRelationships: – BibEntity: Dates: – D: 29 M: 01 Type: published Y: 2021 |
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