| 189 |
|
atom force field and non-equilibrium molecular dynamics. Gold |
| 190 |
|
nanoparticles with radii ranging from 10 - 25 \AA\ were created from a |
| 191 |
|
bulk fcc lattice. These particles were passivated with a 50\% |
| 192 |
< |
coverage -- based on (compared with the coverage densities reported by |
| 193 |
< |
Badia \textit{et al.}) of a selection of thiolates. Three |
| 194 |
< |
straight-chain thiolates of varying chain lengths and rigidities were |
| 195 |
< |
utilized. These are summarized in Fig. \ref{fig:structures}. The |
| 196 |
< |
passivated particles were then solvated in hexane. Details on the |
| 197 |
< |
united atom force field are given below and in the supporting |
| 198 |
< |
information. |
| 192 |
> |
coverage (compared with the coverage densities reported by Badia |
| 193 |
> |
\textit{et al.}) of a selection of thiolates. Three straight-chain |
| 194 |
> |
thiolates of varying chain lengths and rigidities were utilized. |
| 195 |
> |
These are summarized in Fig. \ref{fig:structures}. The passivated |
| 196 |
> |
particles were then solvated in hexane. Details on the united atom |
| 197 |
> |
force field are given below and in the supporting information. |
| 198 |
|
|
| 199 |
|
\begin{figure} |
| 200 |
|
\includegraphics[width=\linewidth]{figures/structures} |
| 311 |
|
carbon sites.\cite{TraPPE-UA.alkylbenzenes} These were used for the |
| 312 |
|
thiolate molecules in our simulations, and missing parameters for the |
| 313 |
|
ligands were supplemented using fits described in the supporting |
| 314 |
< |
information. Bonds are typically rigid in TraPPE-UA, so although |
| 315 |
< |
equilibrium bond distances were taken from TraPPE-UA, flexible bonds |
| 316 |
< |
were allowed bond stretching spring constants from the OPLS-AA force |
| 317 |
< |
field.\cite{Jorgensen:1996sf} |
| 314 |
> |
information. Bonds are rigid in TraPPE-UA, so although equilibrium |
| 315 |
> |
bond distances were taken from this force field, flexible bonds were |
| 316 |
> |
implemented using bond stretching spring constants adapted from the |
| 317 |
> |
OPLS-AA force field.\cite{Jorgensen:1996sf} |
| 318 |
|
|
| 319 |
|
To derive suitable parameters for the thiolates adsorbed on Au(111) |
| 320 |
|
surfaces, we adopted the S parameters from Luedtke and |
| 341 |
|
Gold nanospheres with radii ranging from 10 - 25 \AA\ were created |
| 342 |
|
from a bulk fcc lattice and were thermally equilibrated prior to the |
| 343 |
|
addition of ligands. A 50\% coverage of ligands (based on coverages |
| 344 |
< |
reported by Badia, \textit{et al.}\cite{Badia1996:2}) were placed on |
| 344 |
> |
reported by Badia, \textit{et al.}\cite{Badia1996:2}) was placed on |
| 345 |
|
the surface of the equilibrated nanoparticles using |
| 346 |
|
Packmol\cite{packmol}. We have chosen three lengths for the |
| 347 |
|
straight-chain ligands, $C_4$, $C_8$, and $C_{12}$, differentiated by |
| 352 |
|
thiolate with one double bond in the penultimate (solvent-facing) |
| 353 |
|
carbon-carbon location. The most rigid ligands are fully-conjugated |
| 354 |
|
chains where all of the carbons are represented with conjugated (aryl) |
| 355 |
< |
united-atom carbon atoms (CHar or terminal CH2ar). |
| 355 |
> |
united-atom carbon atoms (CHar or terminal \ce{CH2ar}). |
| 356 |
|
|
| 357 |
|
The nanoparticle / ligand complexes were thermally equilibrated to |
| 358 |
|
allow for ligand conformational flexibility. Packmol was then used to |
