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Molecular Dynamics Studies of Liquid and Chain Systems

Simmons, Vernon (2004) Molecular Dynamics Studies of Liquid and Chain Systems. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Molecular Dynamics simulation has been used for the past 20 - 30 years to study interfacial properties of liquids though the foundations for these studies were laid as far back as 1791 when the astronomer Joseph Dalambre used the time reversible algorithm, commonly called the Verlet algorithm, for the integration of Newton's equations. Some of the properties obtained from Molecular Dynamics, commonly called MD, simulation are density profiles, system configurations, as well as stress or pressure tensor profiles. Generally, the surface tension has been calculated by integrating the stress tensor profile over the width of the interfacial region. In an effort to circumvent the stress tensor calculation and the technical difficulties associated with extensions to include many-body interactions, I will study the feasibility of implementing an equality recently developed by C. Jarzynski to determine the equilibrium surface free energy and, subsequently, the surface tension of an immiscible L-J fluid from an ensemble average of a set of non-equilibrium simulations. In addition to exploring suitable systems for this study, we explore relative computational efficiency of the second method. We also compare the equilibrium free energy difference computed by the Jarzynski method to the apparent free energy difference computed by the Irving-Kirkwood (IK1) approach. We conclude first that both the Jarzynski and IK1 approaches can be useful tools in simulating immiscible liquid systems. The Jarzynski relation is quite effective at extracting free energy differences associated with interfacial area changes in systems comprised of closely spaced, interacting interfaces. For isolated interfaces, the IK1 method is still the best approach for obtaining interfacial tension. We also find that a fast switching Jarzynski algorithm is as efficient and much less costly to implement than a slow switching method.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairCoalson, Robertrob@ringo.chem.pitt.eduCOALSON
Committee MemberLevy, Jeremyjlevy@pitt.eduJLEVY
Committee MemberThompson, Juliajth@pitt.eduJTH
Committee MemberJohnsen, Rainerrj@pitt.eduRJ
Committee MemberDytman, Stevendytman@pitt.eduDYTMAN
Committee MemberGoldschmidt, Yadin Yyadin@pitt.eduYADIN
Date: 5 October 2004
Date Type: Completion
Defense Date: 26 April 2004
Approval Date: 5 October 2004
Submission Date: 17 August 2004
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Immiscible Liquid; Molecular Dynamics; simulation
Other ID:, etd-08172004-212518
Date Deposited: 10 Nov 2011 19:59
Last Modified: 15 Nov 2016 13:49


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