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postgraduate thesis: Development of polarizable water models
Title  Development of polarizable water models 

Authors  
Issue Date  2015 
Publisher  The University of Hong Kong (Pokfulam, Hong Kong) 
Citation  Cao, B. [曹蓓]. (2015). Development of polarizable water models. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5481879 
Abstract  Polarization plays a significant role in the physical and chemical properties of water, thus polarizable water models have been extensively evolved and studied in the past several decades. In this dissertation, two polarizable water models have been extended, and some physical properties in gas phase and condensed phase were studied and analyzed. It was verified that the outofplane polarization effect is of great importance in some physical properties. Besides, we proved that there are some connections between these two models, although they were derived from different methodologies.
The first polarizable water model we developed was a combination of charge response kernel (CRK) method and polarizable point dipole (PPD) method. In the CRK method, a CRK matrix is defined as the second order derivative of energy with respect to the external potential at atomic sites. It is applied to represent the intensity of charge response to external environment. While in the PPD method, the polarizability tensor which is the second order derivative of energy with respect to external field at the same site, is introduced to characterize the variation of dipole moment in the presence of external perturbation. In our method, we proved that although the CRK matrix of threesite water model has 9 element, it only carries two independent variables, and these two variables only rely on the water geometry and the inplane polarizability. Thus besides the CRK matrix located on each atomic site, an additional polarizability residing on oxygen atom specifically inducing dipole moment along the direction perpendicular to the water plane was added in our model. With the addition of the outofplane description, some physical properties were much enhanced.
In the second polarizable water model we extended, electronegativity equalization (EE) method was employed. In this threesite water model, atomic electronegativity and hardness matrix were the first and second order derivative of energy with respect to the partial charge on atomic sites, respectively. In this method, electronegativity differs among different atom types, and the offdiagonal elements in hardness matrix are related on not only atom types but also distances among the corresponding atoms. Accordingly, the intramolecular water deformation can be included. Thus flexible polarizable water model is accessible. With flexibility, this water model is more realistic. Our model validated that more flexible parameterization and geometry could improve the physical performance. At last, we connected the second polarizable water model with the first one. Although the two polarizable models were derived from different methodologies, we proved that under one simple approximation, corresponding CRK matrix can be achieved from hardness matrix. 
Degree  Doctor of Philosophy 
Subject  Water chemistry Intermolecular forces Electron interactions 
Dept/Program  Chemistry 
Persistent Identifier  http://hdl.handle.net/10722/211115 
HKU Library Item ID  b5481879 
DC Field  Value  Language 

dc.contributor.author  Cao, Bei   
dc.contributor.author  曹蓓   
dc.date.accessioned  20150707T23:10:41Z   
dc.date.available  20150707T23:10:41Z   
dc.date.issued  2015   
dc.identifier.citation  Cao, B. [曹蓓]. (2015). Development of polarizable water models. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5481879   
dc.identifier.uri  http://hdl.handle.net/10722/211115   
dc.description.abstract  Polarization plays a significant role in the physical and chemical properties of water, thus polarizable water models have been extensively evolved and studied in the past several decades. In this dissertation, two polarizable water models have been extended, and some physical properties in gas phase and condensed phase were studied and analyzed. It was verified that the outofplane polarization effect is of great importance in some physical properties. Besides, we proved that there are some connections between these two models, although they were derived from different methodologies. The first polarizable water model we developed was a combination of charge response kernel (CRK) method and polarizable point dipole (PPD) method. In the CRK method, a CRK matrix is defined as the second order derivative of energy with respect to the external potential at atomic sites. It is applied to represent the intensity of charge response to external environment. While in the PPD method, the polarizability tensor which is the second order derivative of energy with respect to external field at the same site, is introduced to characterize the variation of dipole moment in the presence of external perturbation. In our method, we proved that although the CRK matrix of threesite water model has 9 element, it only carries two independent variables, and these two variables only rely on the water geometry and the inplane polarizability. Thus besides the CRK matrix located on each atomic site, an additional polarizability residing on oxygen atom specifically inducing dipole moment along the direction perpendicular to the water plane was added in our model. With the addition of the outofplane description, some physical properties were much enhanced. In the second polarizable water model we extended, electronegativity equalization (EE) method was employed. In this threesite water model, atomic electronegativity and hardness matrix were the first and second order derivative of energy with respect to the partial charge on atomic sites, respectively. In this method, electronegativity differs among different atom types, and the offdiagonal elements in hardness matrix are related on not only atom types but also distances among the corresponding atoms. Accordingly, the intramolecular water deformation can be included. Thus flexible polarizable water model is accessible. With flexibility, this water model is more realistic. Our model validated that more flexible parameterization and geometry could improve the physical performance. At last, we connected the second polarizable water model with the first one. Although the two polarizable models were derived from different methodologies, we proved that under one simple approximation, corresponding CRK matrix can be achieved from hardness matrix.   
dc.language  eng   
dc.publisher  The University of Hong Kong (Pokfulam, Hong Kong)   
dc.relation.ispartof  HKU Theses Online (HKUTO)   
dc.rights  Creative Commons: Attribution 3.0 Hong Kong License   
dc.rights  The author retains all proprietary rights, (such as patent rights) and the right to use in future works.   
dc.subject.lcsh  Water chemistry   
dc.subject.lcsh  Intermolecular forces   
dc.subject.lcsh  Electron interactions   
dc.title  Development of polarizable water models   
dc.type  PG_Thesis   
dc.identifier.hkul  b5481879   
dc.description.thesisname  Doctor of Philosophy   
dc.description.thesislevel  Doctoral   
dc.description.thesisdiscipline  Chemistry   
dc.description.nature  published_or_final_version   