--- trunk/COonPt/COonPtAu.tex	2013/03/21 15:28:49	3887
+++ trunk/COonPt/COonPtAu.tex	2013/06/05 21:22:46	3892
@@ -4,6 +4,7 @@
 \usepackage{natbib}
 \usepackage{multirow}
 \usepackage{wrapfig}
+\usepackage{fixltx2e}
 %\mciteErrorOnUnknownfalse
 
 \usepackage[version=3]{mhchem}  % this is a great package for formatting chemical reactions
@@ -323,7 +324,7 @@ an effect on binding energies and binding site prefere
   \hline
   & Calculated & Experimental \\
   \hline
-  \multirow{2}{*}{\textbf{Pt-CO}} & \multirow{2}{*}{-1.9} & -1.4 \bibpunct{}{}{,}{n}{}{,}
+  \multirow{2}{*}{\textbf{Pt-CO}} & \multirow{2}{*}{-1.84} & -1.4 \bibpunct{}{}{,}{n}{}{,}
   (Ref. \protect\cite{Kelemen:1979}) \\
  & &  -1.9 \bibpunct{}{}{,}{n}{}{,} (Ref. \protect\cite{Yeo}) \\ \hline
   \textbf{Au-CO} & -0.39 & -0.40 \bibpunct{}{}{,}{n}{}{,}  (Ref. \protect\cite{TPDGold}) \\
@@ -331,7 +332,75 @@ an effect on binding energies and binding site prefere
 \end{tabular}
 \label{tab:co_energies}
 \end{table}
+
 
+\subsection{Forcefield validation}
+The CO-metal cross interactions were compared directly to DFT results
+found in the supporting information of Tao {\it et al.}
+\cite{Tao:2010} These calculations are estimates of the stabilization
+energy provided to double-layer reconstructions of the perfect 557
+surface by an overlayer of CO molecules in a $c (2 \times 4)$ pattern.
+To make the comparison, metal slabs that were five atoms thick and
+which displayed a 557 facet were constructed.  Double-layer
+(reconstructed) systems were created using six atomic layers where
+enough of a layer was removed from both exposed 557 facets to create
+the double step.  In all cases, the metal slabs contained 480 atoms
+and were minimized using steepest descent under the EAM force
+field. Both the bare metal slabs and slabs with 50\% carbon monoxide
+coverage (arranged in the $c (2 \times 4)$ pattern) were used.  The
+systems are periodic along and perpendicular to the step-edge axes
+with a large vacuum above the displayed 557 facet.
+
+Energies using our force field for the various systems are displayed
+in Table ~\ref{tab:steps}.  The relative energies are calculated as
+$E_{relative} = E_{system} - E_{M-557-S} - N_{CO} E_{CO-M}$,
+where $E_{CO-M}$ is -1.84 eV for CO-Pt and -0.39 eV for CO-Au. For
+platinum, the bare double layer is slightly less stable then the
+original single (557) step. However, addition of carbon monoxide
+stabilizes the reconstructed double layer relative to the perfect 557.
+This result is in qualitative agreement with DFT calculations in Tao
+{\it et al.}\cite{Tao:2010}, who also showed that the addition of CO
+leads to a reversal in stability.
+
+The DFT calculations suggest an increased stability of 0.08 kcal/mol
+(0.7128 eV) per Pt atom for going from the single to double step
+structure in the presence of carbon monoxide. 
+
+The gold systems show much smaller energy differences between the
+single and double layers. The weaker binding of CO to Au is evidenced
+by the much smaller change in relative energy between the structures
+when carbon monoxide is present.  Additionally, as CO-Au binding is
+much weaker than CO-Pt, it would be unlikely that CO would approach
+the 50\% coverage levels operating temperatures for the gold surfaces.
+
+%Table of single step double step calculations
+\begin{table}[H]
+  \caption{Minimized single point energies of (S)ingle and (D)ouble
+    steps.  The addition of CO in a 50\% $c(2 \times 4)$ coverage acts as a
+    stabilizing presence and suggests a driving force for the observed
+    reconstruction on the highest coverage Pt system. All energies are
+    in kcal/mol.} 
+\centering
+\begin{tabular}{| c | c | c | c | c | c |}
+\hline
+\textbf{Step} & \textbf{N}\textsubscript{M} & \textbf{N\textsubscript{CO}} & \textbf{Relative Energy} & \textbf{$\Delta$E/M} & \textbf{$\Delta$E/CO} \\
+\hline
+Pt(557)-S & 480 & 0 & 0 & 0 & - \\
+Pt(557)-D & 480 & 0 & 114.783 & 0.239 & -\\
+Pt(557)-S & 480 & 40 & -124.546 & -0.259 & -3.114\\
+Pt(557)-D & 480 & 44 & -34.953 & -0.073 & -0.794\\
+\hline
+\hline
+Au(557)-S & 480 & 0 & 0 & 0 & - \\
+Au(557)-D & 480 & 0 & 79.572 & 0.166 & - \\
+Au(557)-S & 480 & 40 & -157.199 & -0.327 & -3.930\\
+Au(557)-D & 480 & 44 & -123.297 & -0.257 & -2.802 \\
+\hline
+\end{tabular}
+\label{tab:steps}
+\end{table}
+
+
 \subsection{Pt(557) and Au(557) metal interfaces}
 Our Pt system is an orthorhombic periodic box of dimensions
 54.482~x~50.046~x~120.88~\AA~while our Au system has 
