| 661 |
|
Generation of the system configurations was dependent on the system |
| 662 |
|
type. For the solid and liquid water configurations, configuration |
| 663 |
|
snapshots were taken at regular intervals from higher temperature 1000 |
| 664 |
< |
SPC/E water molecule trajectories and each equilibrated individually. |
| 665 |
< |
The solid and liquid NaCl systems consisted of 500 Na+ and 500 Cl- |
| 666 |
< |
ions and were selected and equilibrated in the same fashion as the |
| 667 |
< |
water systems. For the low and high ionic strength NaCl solutions, 4 |
| 668 |
< |
and 40 ions were first solvated in a 1000 water molecule boxes |
| 669 |
< |
respectively. Ion and water positions were then randomly swapped, and |
| 670 |
< |
the resulting configurations were again equilibrated individually. |
| 671 |
< |
Finally, for the Argon/Water "charge void" systems, the identities of |
| 672 |
< |
all the SPC/E waters within 6 \AA\ of the center of the equilibrated |
| 673 |
< |
water configurations were converted to argon |
| 674 |
< |
(Fig. \ref{fig:argonSlice}). |
| 664 |
> |
SPC/E water molecule trajectories and each equilibrated |
| 665 |
> |
individually.\cite{Berendsen87} The solid and liquid NaCl systems |
| 666 |
> |
consisted of 500 Na+ and 500 Cl- ions and were selected and |
| 667 |
> |
equilibrated in the same fashion as the water systems. For the low |
| 668 |
> |
and high ionic strength NaCl solutions, 4 and 40 ions were first |
| 669 |
> |
solvated in a 1000 water molecule boxes respectively. Ion and water |
| 670 |
> |
positions were then randomly swapped, and the resulting configurations |
| 671 |
> |
were again equilibrated individually. Finally, for the Argon/Water |
| 672 |
> |
"charge void" systems, the identities of all the SPC/E waters within 6 |
| 673 |
> |
\AA\ of the center of the equilibrated water configurations were |
| 674 |
> |
converted to argon (Fig. \ref{fig:argonSlice}). |
| 675 |
|
|
| 676 |
|
\begin{figure} |
| 677 |
|
\centering |
| 726 |
|
|
| 727 |
|
In this figure, it is apparent that it is unreasonable to expect |
| 728 |
|
realistic results using an unmodified cutoff. This is not all that |
| 729 |
< |
surprising since this results in large energy fluctuations as atoms |
| 730 |
< |
move in and out of the cutoff radius. These fluctuations can be |
| 731 |
< |
alleviated to some degree by using group based cutoffs with a |
| 732 |
< |
switching function.\cite{Steinbach94} The Group Switch Cutoff row |
| 733 |
< |
doesn't show a significant improvement in this plot because the salt |
| 734 |
< |
and salt solution systems contain non-neutral groups, see the |
| 729 |
> |
surprising since this results in large energy fluctuations as atoms or |
| 730 |
> |
molecules move in and out of the cutoff radius.\cite{Rahman71,Adams79} |
| 731 |
> |
These fluctuations can be alleviated to some degree by using group |
| 732 |
> |
based cutoffs with a switching |
| 733 |
> |
function.\cite{Adams79,Steinbach94,Leach01} The Group Switch Cutoff |
| 734 |
> |
row doesn't show a significant improvement in this plot because the |
| 735 |
> |
salt and salt solution systems contain non-neutral groups, see the |
| 736 |
|
accompanying supporting information for a comparison where all groups |
| 737 |
|
are neutral. |
| 738 |
|
|
