--- interfacial/interfacial.tex 2011/09/23 17:31:50 3761 +++ interfacial/interfacial.tex 2011/09/27 21:02:48 3763 @@ -123,7 +123,13 @@ number of hydrophobic and hydrophilic aqueous interfac Garde and coworkers\cite{garde:nl2005,garde:PhysRevLett2009} applied this approach to various liquid interfaces and studied how thermal conductance (or resistance) is dependent on chemical details of a -number of hydrophobic and hydrophilic aqueous interfaces. +number of hydrophobic and hydrophilic aqueous interfaces. {\bf And + Luo {\it et al.} studied the thermal conductance of Au-SAM-Au + junctions using the same approach, with comparison to a constant + temperature difference method\cite{Luo20101}. While this latter + approach establishes more thermal distributions compared to the + former RNEMD methods, it does not guarantee momentum or kinetic + energy conservations.} Recently, we have developed a Non-Isotropic Velocity Scaling (NIVS) algorithm for RNEMD simulations\cite{kuang:164101}. This algorithm @@ -137,10 +143,12 @@ properties. Different models were used for both the ca The work presented here deals with the Au(111) surface covered to varying degrees by butanethiol, a capping agent with short carbon chain, and solvated with organic solvents of different molecular -properties. Different models were used for both the capping agent and -the solvent force field parameters. Using the NIVS algorithm, the -thermal transport across these interfaces was studied and the -underlying mechanism for the phenomena was investigated. +properties. {\bf To our knowledge, few previous MD inverstigations + have been found to address to these systems yet.} Different models +were used for both the capping agent and the solvent force field +parameters. Using the NIVS algorithm, the thermal transport across +these interfaces was studied and the underlying mechanism for the +phenomena was investigated. \section{Methodology} \subsection{Imposed-Flux Methods in MD Simulations} @@ -836,7 +844,7 @@ a simulation. Since the interface persisted in these surfaces 90\% covered by butanethiols, but did not see this above phenomena even at $\langle T\rangle\sim$300K. That said, we did observe butanethiols migrating to neighboring three-fold sites during -a simulation. Since the interface persisted in these simulations, +a simulation. Since the interface persisted in these simulations, we were able to obtain $G$'s for these interfaces even at a relatively high temperature without being affected by surface reconstructions. @@ -880,7 +888,10 @@ interfaces. surface Au layer to the capping agents. Therefore, in our simulations, the Au / S interfaces do not appear to be the primary barrier to thermal transport when compared with the butanethiol / solvent -interfaces. +interfaces. {\bf This confirms the results from Luo {\it et + al.}\cite{Luo20101}, which reported $G$ for Au-SAM junctions + generally twice larger than what we have computed for the + thiol-liquid interfaces.} \begin{figure} \includegraphics[width=\linewidth]{vibration} @@ -906,7 +917,11 @@ in the UA force field. vibrations were treated classically. The presence of extra degrees of freedom in the AA force field yields higher heat exchange rates between the two phases and results in a much higher conductivity than -in the UA force field. +in the UA force field. {\bf Due to the classical models used, this + even includes those high frequency modes which should be unpopulated + at our relatively low temperatures. This artifact causes high + frequency vibrations accountable for thermal transport in classical + MD simulations.} The similarity in the vibrational modes available to solvent and capping agent can be reduced by deuterating one of the two components @@ -1011,6 +1026,11 @@ Dame. Foundation under grant CHE-0848243. Computational time was provided by the Center for Research Computing (CRC) at the University of Notre Dame. + +\section{Supporting Information} +This information is available free of charge via the Internet at +http://pubs.acs.org. + \newpage \bibliography{interfacial}