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Cation Solvation in Water and Acetonitrile from Theoretical Calculations
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Metal ions solvated in aqueous, non-aqueous, and mixtures of solvents occur in many chemical contexts, for example in electrochemical applications and solvent separation. Solvated ions appear in high concentration in the living organisms, where their presence or absence can fundamentally alter the functions of life. In many of these cases, understanding the selective solvation and the dynamics of the ions is essential for the understanding of the processes involved.

Computer simulation provides a molecular level of detail of the solvation process usually not available from experiments. The quality of the interaction models employed in the theoretical description is of particular importance, since even rather small changes in the interaction can lead to substantial and qualitative differences.

This thesis describes the development of a sequence of increasingly refined analytical ion-solvent potentials from ab initio calculations for the systems Li+(aq), Na+(aq), Mg2+(aq), Al3+(aq), Li+(MeCN), Na+(MeCN), Li+(aq, MeCN), and Na+(aq, MeCN). Molecular dynamics simulations using these potentials were subsequently performed, and some key-properties computed. The reliability of the computed thermodynamical, structural and dynamical properties was scrutinized.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2003. , p. 45
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 892
Keywords [en]
Inorganic chemistry, molecular dynamics, ab initio, lithium, sodium, magnesium, aluminum, metal ion, water, acetonitrile, solution, solvation
Keywords [sv]
Oorganisk kemi
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-3598ISBN: 91-554-5751-7 (print)OAI: oai:DiVA.org:uu-3598DiVA, id: diva2:163396
Public defence
2003-10-24, 2001, The Ångström Laboratory, Uppsala, 10:15
Opponent
Supervisors
Available from: 2003-10-03 Created: 2003-10-03 Last updated: 2013-07-24Bibliographically approved
List of papers
1. Pressure dependence and activation volume for the water exchange mechanism in NaCl(aq) from MD simulations
Open this publication in new window or tab >>Pressure dependence and activation volume for the water exchange mechanism in NaCl(aq) from MD simulations
1997 In: Chemical Physics Letters, Vol. 276, p. 114-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-90882 (URN)
Available from: 2003-10-03 Created: 2003-10-03Bibliographically approved
2. Effective three-body potentials for Li+(aq) and Mg2+(aq)
Open this publication in new window or tab >>Effective three-body potentials for Li+(aq) and Mg2+(aq)
2003 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 119, no 14, p. 7263-Article in journal (Refereed) Published
Abstract [en]

A method for the extraction of effective three-body potential parameters from high-level ab initio cluster calculations is presented and compared to effective pair potentials extracted at the same level. Dilute Li+(aq) and Mg2+(aq) solutions are used as test cases and long molecular-dynamics simulations using these newly developed potentials were performed. Resulting thermodynamical, structural, and dynamical properties are compared to experiment as well as to the empirical effective pair potentials of Åqvist. Moreover, a new time-saving method for the correction of cluster energies computed with a relatively cheap ab initio method, to yield expensive, high-level ab initio energies, is presented. The effective pair approach is shown to give inconsistent results when compared to the effective three-body potentials. The performance of three different charge compensation methods (uniform charge plasm, Bogusz net charge correction, and counter ions) is compared for a large number of different system sizes. For most properties studied here, the system-size dependence is found to be small for system sizes with 256 water molecules or more. However, for the self-diffusion coefficients, a 1/L dependence is found, i.e., a very large system-size dependence. A very simple method for correcting for this deficiency is proposed. The results for most properties are found to compare reasonably well to experiment when using the effective three-body potentials.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-46241 (URN)10.1063/1.1604372 (DOI)
Available from: 2006-03-21 Created: 2006-03-21 Last updated: 2017-12-05Bibliographically approved
3. Rate and Mechanisms for Water Exchange around Li+(aq) from MD Simulations
Open this publication in new window or tab >>Rate and Mechanisms for Water Exchange around Li+(aq) from MD Simulations
2003 In: Journal of Physical Chemistry B, Vol. 107, no 18, p. 4470-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-90884 (URN)
Available from: 2003-10-03 Created: 2003-10-03Bibliographically approved
4. Many-body potentials for aqueous Li+, Na+, Mg2+ and Al3+: Comparison of effective three-body potentials and poliarizable models
Open this publication in new window or tab >>Many-body potentials for aqueous Li+, Na+, Mg2+ and Al3+: Comparison of effective three-body potentials and poliarizable models
2004 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 120, no 10, p. 4829-4843Article in journal (Refereed) Published
Abstract [en]

Many-body potentials for the aqueous Li+, Na+, Mg2+, and Al3+ ions have been constructed from ab initio cluster calculations. Pure pair, effective pair, effective three-body, and effective polarizable models were created and used in subsequent molecular dynamics simulations. The structures of the first and second solvation shells were studied using radial distribution functions and angular-radial distribution functions. The effective three-body and polarizable potentials yield similar first-shell structures, while the contraction of the O–O distances between the first and second solvation shells is more pronounced with the polarizable potentials. The definition of the tilt angle of the water molecules around the ions is discussed. When a proper definition is used, it is found that for Li+, Mg2+, and Al3+ the water molecules prefer a trigonal orientation, but for Na+ a tetrahedral orientation (ion in lone-pair direction) is preferred. The self-diffusion coefficients for the water molecules and the ions were calculated; the ionic values follow the order obtained from experiment, although the simulated absolute values are smaller than experiment for Mg2+ and Al3+.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-67824 (URN)10.1063/1.1641191 (DOI)
Available from: 2006-03-21 Created: 2006-03-21 Last updated: 2017-11-21Bibliographically approved
5. The solvation of Li+ and Na+ in acetonitrile from ab initio-derived many-body ion-solvent potentials
Open this publication in new window or tab >>The solvation of Li+ and Na+ in acetonitrile from ab initio-derived many-body ion-solvent potentials
In: Chemical PhysicsArticle in journal (Refereed) Submitted
Identifiers
urn:nbn:se:uu:diva-90886 (URN)
Available from: 2003-10-03 Created: 2003-10-03Bibliographically approved
6. Solvation of Li+ and Na+ in mixed water / acetonitrile solution from MD simulations employing many-body potentials
Open this publication in new window or tab >>Solvation of Li+ and Na+ in mixed water / acetonitrile solution from MD simulations employing many-body potentials
Manuscript (Other academic)
Identifiers
urn:nbn:se:uu:diva-90887 (URN)
Available from: 2003-10-03 Created: 2003-10-03 Last updated: 2010-01-13Bibliographically approved

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