Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface
This dissertation consists of two independent parts: Part I. methane hydrate, and Part II. water loading on a clay surface. In Part I (chapter 2-3), we conducted molecular dynamics simulations with non-polarizable force fields to study structural and thermal properties of methane hydrate. We show th...
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ftunivpittsburgh:oai:d-scholarship.pitt.edu:13633 2023-09-05T13:21:06+02:00 Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface Zhang, Guozhen 2012-10-09 application/pdf http://d-scholarship.pitt.edu/13633/ http://d-scholarship.pitt.edu/13633/1/ETD_zgz.v2.pdf en eng http://d-scholarship.pitt.edu/13633/1/ETD_zgz.v2.pdf Zhang, Guozhen (2012) Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface. Doctoral Dissertation, University of Pittsburgh. (Unpublished) University of Pittsburgh ETD PeerReviewed 2012 ftunivpittsburgh 2023-08-14T17:31:08Z This dissertation consists of two independent parts: Part I. methane hydrate, and Part II. water loading on a clay surface. In Part I (chapter 2-3), we conducted molecular dynamics simulations with non-polarizable force fields to study structural and thermal properties of methane hydrate. We show that the TIP4P/Ice and TIP4P/2005 model potentials do well in the description of the lattice constant and radial distribution functions. Yet they, together with SPC/E and TIP4P models, overestimate the thermal expansion coefficient due to the inadequate description of the non-linear response of lattice constant to temperature. We also show that TIP4P/Ice and TIP4P/2005 overestimate the decomposition temperature of methane hydrate from the experimental value by 50 K and 30 K respectively, while SPC/E gives a good estimation deviating by about 5 K. All these force fields are found to overestimate the thermal conductivity of methane hydrate, but they are able to describe the weak temperature dependence from 100 to 150 K and 225 to 270 K. It is also found that all initial structures used in the work have a proton ordering tendency, suggesting a potential role of proton arrangement in the temperature dependence of the thermal conductivity. In part II (chapter 4), we conducted dispersion-corrected density function theory (DFT-D) and classical force field calculations to study the water loading on a pyrophyllite (001) surface. We disclose low-energy binding motifs from one water molecule to six water molecules and reinterpret the hydrophobic nature of the pyrophyllite surface from the point of view that a water molecule prefers to interact with other water molecules than to be bound on the surface. The force field approach, while providing a similar trend of the water binding to the DFT-D result, predicts some low-energy binding motifs which are not confirmed by the DFT-D calculation. It suggests a refinement of the force field to better describe the interfacial orientation of water on a clay surface. Thesis Methane hydrate University of Pittsburgh: D-Scholarship@Pitt |
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University of Pittsburgh: D-Scholarship@Pitt |
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ftunivpittsburgh |
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English |
description |
This dissertation consists of two independent parts: Part I. methane hydrate, and Part II. water loading on a clay surface. In Part I (chapter 2-3), we conducted molecular dynamics simulations with non-polarizable force fields to study structural and thermal properties of methane hydrate. We show that the TIP4P/Ice and TIP4P/2005 model potentials do well in the description of the lattice constant and radial distribution functions. Yet they, together with SPC/E and TIP4P models, overestimate the thermal expansion coefficient due to the inadequate description of the non-linear response of lattice constant to temperature. We also show that TIP4P/Ice and TIP4P/2005 overestimate the decomposition temperature of methane hydrate from the experimental value by 50 K and 30 K respectively, while SPC/E gives a good estimation deviating by about 5 K. All these force fields are found to overestimate the thermal conductivity of methane hydrate, but they are able to describe the weak temperature dependence from 100 to 150 K and 225 to 270 K. It is also found that all initial structures used in the work have a proton ordering tendency, suggesting a potential role of proton arrangement in the temperature dependence of the thermal conductivity. In part II (chapter 4), we conducted dispersion-corrected density function theory (DFT-D) and classical force field calculations to study the water loading on a pyrophyllite (001) surface. We disclose low-energy binding motifs from one water molecule to six water molecules and reinterpret the hydrophobic nature of the pyrophyllite surface from the point of view that a water molecule prefers to interact with other water molecules than to be bound on the surface. The force field approach, while providing a similar trend of the water binding to the DFT-D result, predicts some low-energy binding motifs which are not confirmed by the DFT-D calculation. It suggests a refinement of the force field to better describe the interfacial orientation of water on a clay surface. |
format |
Thesis |
author |
Zhang, Guozhen |
spellingShingle |
Zhang, Guozhen Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface |
author_facet |
Zhang, Guozhen |
author_sort |
Zhang, Guozhen |
title |
Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface |
title_short |
Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface |
title_full |
Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface |
title_fullStr |
Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface |
title_full_unstemmed |
Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface |
title_sort |
computational studies of chemical systems: i. a molecular dynamics simulation of methane hydrate; ii. theoretical investigation of water loading on a pyrophyllite (001) surface |
publishDate |
2012 |
url |
http://d-scholarship.pitt.edu/13633/ http://d-scholarship.pitt.edu/13633/1/ETD_zgz.v2.pdf |
genre |
Methane hydrate |
genre_facet |
Methane hydrate |
op_relation |
http://d-scholarship.pitt.edu/13633/1/ETD_zgz.v2.pdf Zhang, Guozhen (2012) Computational Studies of Chemical Systems: I. A Molecular Dynamics Simulation of Methane Hydrate; II. Theoretical Investigation of Water Loading on a Pyrophyllite (001) Surface. Doctoral Dissertation, University of Pittsburgh. (Unpublished) |
_version_ |
1776201715750535168 |