Link to the University of Pittsburgh Homepage
Link to the University Library System Homepage Link to the Contact Us Form

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) 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 (Unpublished)

PDF (dissertation)
Primary Text

Download (3MB) | Preview


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.


Social Networking:
Share |


Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairJordan, Kennethjordan@pitt.eduJORDAN
Committee MemberChong, Lilianltchong@pitt.eduLTCHONG
Committee MemberLiu, Haitaohliu@pitt.eduHLIU
Committee MemberMcGaughey,
Date: 9 October 2012
Date Type: Publication
Defense Date: 15 June 2012
Approval Date: 9 October 2012
Submission Date: 17 August 2012
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 132
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: molecular dynamics, thermal conductivity, methane hydrate, density functional theory, clay surface, hydrophobicity
Date Deposited: 09 Oct 2012 14:06
Last Modified: 15 Nov 2016 14:02


Monthly Views for the past 3 years

Plum Analytics

Actions (login required)

View Item View Item