| 458 |
|
\begin{figure} |
| 459 |
|
\centering |
| 460 |
|
\includegraphics[width=2.5in]{./figures/corrDiag.pdf} |
| 461 |
< |
\caption{ An illustration of angles involved in the correlations observed in figure \ref{fig:contour}.} |
| 461 |
> |
\caption{ An illustration of angles involved in the correlations |
| 462 |
> |
observed in figure \ref{fig:contour}.} |
| 463 |
|
\label{fig:corrAngle} |
| 464 |
|
\end{figure} |
| 465 |
|
|
| 898 |
|
properties change. |
| 899 |
|
|
| 900 |
|
\begin{table} |
| 901 |
< |
\caption{PROPERTIES OF SSD/RF WHEN USING DIFFERENT ELECTROSTATIC CORRECTION METHODS} |
| 901 |
> |
\caption{PROPERTIES OF SSD/RF WHEN USING DIFFERENT ELECTROSTATIC |
| 902 |
> |
CORRECTION METHODS} |
| 903 |
|
\footnotesize |
| 904 |
|
\centering |
| 905 |
|
\begin{tabular}{ llccc } |
| 919 |
|
\end{tabular} |
| 920 |
|
\label{tab:dampedSSDRF} |
| 921 |
|
\end{table} |
| 922 |
+ |
|
| 923 |
+ |
The properties shown in table \ref{tab:dampedSSDRF} compare |
| 924 |
+ |
surprisingly well. The average density shows a modest increase when |
| 925 |
+ |
using damped electrostatics in place of the reaction field. This comes |
| 926 |
+ |
about because we neglect the pressure effect due to the surroundings |
| 927 |
+ |
outside of the cuttoff, instead relying on screening effects to |
| 928 |
+ |
neutralize electrostatic interactions at long distances. The $C_p$ |
| 929 |
+ |
also shows a slight increase, indicating greater fluctuation in the |
| 930 |
+ |
enthalpy at constant pressure. The only other differences between the |
| 931 |
+ |
damped and reaction field results are the dipole reorientational time |
| 932 |
+ |
constants, $\tau_1$ and $\tau_2$. When using damped electrostatics, |
| 933 |
+ |
the water molecules relax more quickly and are almost identical to the |
| 934 |
+ |
experimental values. These results indicate that not only is it |
| 935 |
+ |
reasonable to use damped electrostatics with SSD/RF, it is recommended |
| 936 |
+ |
if capturing realistic dynamics is of primary importance. This is an |
| 937 |
+ |
encouraging result because of the more varied applicability of damping |
| 938 |
+ |
over the reaction field technique. Rather than be limited to |
| 939 |
+ |
homogeneous systems, SSD/RF can be used effectively with mixed |
| 940 |
+ |
systems, such as dissolved ions, small organic molecules, or even |
| 941 |
+ |
proteins. |
| 942 |
|
|
| 943 |
|
In addition to the properties tabulated in table |
| 944 |
< |
\ref{tab:dampedSSDRF}, we calculated the static dielectric constant |
| 944 |
> |
\ref{tab:dampedSSDRF}, we calculated the static dielectric constant |
| 945 |
|
from a 5ns simulation of SSD/RF using the damped electrostatics. The |
| 946 |
|
resulting value of 82.6(6) compares very favorably with the |
| 947 |
|
experimental value of 78.3.\cite{Malmberg56} This value is closer to |
| 948 |
|
the experimental value than what was expected according to figure |
| 949 |
|
\ref{fig:dielectricMap}, raising some questions as to the accuracy of |
| 950 |
< |
the visual contours in the figure. This simply enforces the |
| 951 |
< |
qualitative nature of contour plotting. |
| 950 |
> |
the visual contours in the figure. This highlights the qualitative |
| 951 |
> |
nature of contour plotting. |
| 952 |
|
|
| 953 |
|
\section{Tetrahedrally Restructured Elongated Dipole (TRED) Water Model} |
| 954 |
|
|
| 955 |
+ |
The SSD/RF model works well with damped electrostatics, but because of its point multipole character, there is no charge neutralization correction at $R_\textrm{c}$. This has the effect of increasing the density, since there is no consideration of the ``surroundings''. |
| 956 |
+ |
|
| 957 |
|
\begin{table} |
| 958 |
|
\caption{PROPERTIES OF TRED COMPARED WITH SSD/RF AND EXPERIMENT} |
| 959 |
|
\footnotesize |
| 964 |
|
& & SSD/RF & TRED & Experiment [Ref.]\\ |
| 965 |
|
& & $\alpha = 0.2125$\AA$^{-1}$ & $\alpha = 0.2125$\AA$^{-1}$ & \\ |
| 966 |
|
\midrule |
| 967 |
< |
$\rho$ & (g cm$^{-3}$) & 1.004(4) & 0.996(4) & 0.997 \cite{CRC80}\\ |
| 968 |
< |
$C_p$ & (cal mol$^{-1}$ K$^{-1}$) & 27(1) & & 18.005 \cite{Wagner02} \\ |
| 967 |
> |
$\rho$ & (g cm$^{-3}$) & 1.004(4) & 0.995(5) & 0.997 \cite{CRC80}\\ |
| 968 |
> |
$C_p$ & (cal mol$^{-1}$ K$^{-1}$) & 27(1) & 23(1) & 18.005 \cite{Wagner02} \\ |
| 969 |
|
$D$ & ($10^{-5}$ cm$^2$ s$^{-1}$) & 2.33(2) & 2.30(5) & 2.299 \cite{Mills73}\\ |
| 970 |
|
$n_C$ & & 4.4 & 5.3 & 4.7 \cite{Hura00}\\ |
| 971 |
|
$n_H$ & & 3.7 & 4.1 & 3.5 \cite{Soper86}\\ |
| 972 |
|
$\tau_1$ & (ps) & 5.86(8) & 6.0(1) & 5.7 \cite{Eisenberg69}\\ |
| 973 |
|
$\tau_2$ & (ps) & 2.45(7) & 2.49(5) & 2.3 \cite{Krynicki66}\\ |
| 974 |
< |
$\epsilon_0$ & & 82.6(6) & & 78.3 \cite{Malmberg56}\\ |
| 975 |
< |
$\tau_D$ & (ps) & & & 8.2(4) \cite{Kindt96}\\ |
| 974 |
> |
$\epsilon_0$ & & 82.6(6) & 83(1) & 78.3 \cite{Malmberg56}\\ |
| 975 |
> |
$\tau_D$ & (ps) & 9.1(2) & 10.6(3) & 8.2(4) \cite{Kindt96}\\ |
| 976 |
|
\bottomrule |
| 977 |
|
\end{tabular} |
| 978 |
|
\label{tab:tredProps} |
