| 209 |
|
|
| 210 |
|
Long-range dipole-dipole interactions were accounted for in this study |
| 211 |
|
by using either the reaction field method or by resorting to a simple |
| 212 |
< |
cubic switching function at a cutoff radius. Under the first method, |
| 213 |
< |
the magnitude of the reaction field acting on dipole $i$ is |
| 212 |
> |
cubic switching function at a cutoff radius. The reaction field |
| 213 |
> |
method was actually first used in Monte Carlo simulations of liquid |
| 214 |
> |
water.\cite{Barker73} Under this method, the magnitude of the reaction |
| 215 |
> |
field acting on dipole $i$ is |
| 216 |
|
\begin{equation} |
| 217 |
|
\mathcal{E}_{i} = \frac{2(\varepsilon_{s} - 1)}{2\varepsilon_{s} + 1} |
| 218 |
|
\frac{1}{r_{c}^{3}} \sum_{j\in{\mathcal{R}}} {\bf \mu}_{j} f(r_{ij})\ , |
| 893 |
|
radial location of the minima following the first solvation shell |
| 894 |
|
peak, and g$(r)$ is either g$_\text{OO}(r)$ or g$_\text{OH}(r)$ for |
| 895 |
|
calculation of the coordination number or hydrogen bonds per particle |
| 896 |
< |
respectively. |
| 896 |
> |
respectively. The number of hydrogen bonds stays relatively constant |
| 897 |
> |
across all of the models, but the coordination numbers of SSD/E and |
| 898 |
> |
SSD/RF show an improvement over SSD1. This improvement is primarily |
| 899 |
> |
due to the widening of the first solvation shell peak, allowing the |
| 900 |
> |
first minima to push outward. Comparing the coordination number with |
| 901 |
> |
the number of hydrogen bonds can lead to more insight into the |
| 902 |
> |
structural character of the liquid. Because of the near identical |
| 903 |
> |
values for SSD1, it appears to be a little too exclusive, in that all |
| 904 |
> |
molecules in the first solvation shell are involved in forming ideal |
| 905 |
> |
hydrogen bonds. The differing numbers for the newly parameterized |
| 906 |
> |
models indicate the allowance of more fluid configurations in addition |
| 907 |
> |
to the formation of an acceptable number of ideal hydrogen bonds. |
| 908 |
|
|
| 909 |
|
The time constants for the self orientational autocorrelation function |
| 910 |
|
are also displayed in Table \ref{liquidproperties}. The dipolar |
| 919 |
|
vector can be calculated from an exponential fit in the long-time |
| 920 |
|
regime ($t > \tau_l^\mu$).\cite{Rothschild84} Calculation of these |
| 921 |
|
time constants were averaged from five detailed NVE simulations |
| 922 |
< |
performed at the STP density for each of the respective models. |
| 922 |
> |
performed at the STP density for each of the respective models. Again, |
| 923 |
> |
SSD/E and SSD/RF show improved behavior over SSD1 both with and |
| 924 |
> |
without an active reaction field. Numbers published from the original |
| 925 |
> |
SSD dynamics studies appear closer to the experimental values, and we |
| 926 |
> |
attribute this discrepancy to the implimentation of an Ewald sum |
| 927 |
> |
versus a reaction field. |
| 928 |
|
|
| 929 |
|
\subsection{Additional Observations} |
| 930 |
|
|
