| 487 |
|
|
| 488 |
|
\begin{figure} |
| 489 |
|
\includegraphics[width=\linewidth]{thermalGrad} |
| 490 |
< |
\caption{NIVS-RNEMD method creates similar temperature gradients |
| 491 |
< |
compared with the swapping method under a variety of imposed kinetic |
| 492 |
< |
energy flux values.} |
| 490 |
> |
\caption{NIVS-RNEMD method (b) creates similar temperature gradients |
| 491 |
> |
compared with the swapping method (a) under a variety of imposed |
| 492 |
> |
kinetic energy flux values. Furthermore, the implementation of |
| 493 |
> |
Non-Isotropic Velocity Scaling does not cause temperature |
| 494 |
> |
difference among the three dimensions (c).} |
| 495 |
|
\label{thermalGrad} |
| 496 |
|
\end{figure} |
| 497 |
|
|
| 503 |
|
relatively high non-physical kinetic energy flux, the speed of |
| 504 |
|
molecules in slabs where swapping occured could deviate from the |
| 505 |
|
Maxwell-Boltzmann distribution. This behavior was also noted by Tenney |
| 506 |
< |
and Maginn.\cite{Maginn:2010} Figure \ref{thermalHist} shows how these |
| 507 |
< |
distributions deviate from an ideal distribution. In the ``hot'' slab, |
| 508 |
< |
the probability density is notched at low speeds and has a substantial |
| 509 |
< |
shoulder at higher speeds relative to the ideal MB distribution. In |
| 506 |
> |
and Maginn\cite{Maginn:2010} in their simulations for shear viscosity |
| 507 |
> |
calculations. Figure \ref{thermalHist} shows how these distributions |
| 508 |
> |
deviate from an ideal distribution. In the ``hot'' slab, the |
| 509 |
> |
probability density is notched at low speeds and has a substantial |
| 510 |
> |
shoulder at higher speeds relative to the ideal MB distribution. In |
| 511 |
|
the cold slab, the opposite notching and shouldering occurs. This |
| 512 |
< |
phenomenon is more obvious at higher swapping rates. |
| 512 |
> |
phenomenon is more obvious at higher swapping rates. |
| 513 |
|
|
| 514 |
|
In the velocity distributions, the ideal Gaussian peak is |
| 515 |
|
substantially flattened in the hot slab, and is overly sharp (with |
| 536 |
|
|
| 537 |
|
\begin{figure} |
| 538 |
|
\includegraphics[width=\linewidth]{thermalHist} |
| 539 |
< |
\caption{Speed distribution for thermal conductivity using a) |
| 540 |
< |
``swapping'' and b) NIVS- RNEMD methods. Shown is from the |
| 541 |
< |
simulations with an exchange or equilvalent exchange interval of 250 |
| 542 |
< |
fs. In circled areas, distributions from ``swapping'' RNEMD |
| 543 |
< |
simulation have deviation from ideal Maxwell-Boltzmann distribution |
| 544 |
< |
(curves fit for each distribution).} |
| 539 |
> |
\caption{Speed distribution for thermal conductivity using |
| 540 |
> |
``swapping'' and NIVS-RNEMD methods. Shown is from simulations under |
| 541 |
> |
${\langle T^* \rangle = 0.8}$ with an swapping interval of 200 |
| 542 |
> |
time steps (equivalent ${J_z^*\sim 0.2}$). In circled areas, |
| 543 |
> |
distributions from ``swapping'' RNEMD simulation have deviations |
| 544 |
> |
from ideal Maxwell-Boltzmann distributions.} |
| 545 |
|
\label{thermalHist} |
| 546 |
|
\end{figure} |
| 547 |
|
|
| 557 |
|
\includegraphics[width=\linewidth]{shear} |
| 558 |
|
\caption{Average momentum gradients in shear viscosity simulations, |
| 559 |
|
using (a) ``swapping'' method and (b) NIVS-RNEMD method |
| 560 |
< |
respectively. (c) Temperature difference among x and y, z dimensions |
| 561 |
< |
observed when using NIVS-RNEMD with equivalent exchange interval of |
| 559 |
< |
500 fs.} |
| 560 |
> |
respectively. (c) Temperature difference among $x$ and $y, z$ |
| 561 |
> |
dimensions observed when using NIVS-RNEMD with ${j_z^*(p_x)\sim 0.09}$.} |
| 562 |
|
\label{shear} |
| 563 |
|
\end{figure} |
| 564 |
|
|
| 608 |
|
momentum transfer to create a gradient, and 1ns was alotted for |
| 609 |
|
data collection under RNEMD. |
| 610 |
|
|
| 611 |
< |
As shown in Figure \ref{spceGrad}, temperature gradients were |
| 612 |
< |
established similar to the previous work. Our simulation results under |
| 613 |
< |
318K are in well agreement with those from Bedrov {\it et al.} (Table |
| 611 |
> |
In our simulations, temperature gradients were established similar to |
| 612 |
> |
the previous work. Our simulation results under 318K are in well |
| 613 |
> |
agreement with those from Bedrov {\it et al.} (Table |
| 614 |
|
\ref{spceThermal}). And both methods yield values in reasonable |
| 615 |
|
agreement with experimental value. A larger difference between |
| 616 |
|
simulation result and experiment is found under 300K. This could |
| 773 |
|
of different identities are segregated in different slabs. To test |
| 774 |
|
this application, we simulated a Gold (111) / water interface. To |
| 775 |
|
construct the interface, a box containing a lattice of 1188 Au atoms |
| 776 |
< |
(with the 111 surface in the +z and -z directions) was allowed to |
| 776 |
> |
(with the 111 surface in the $+z$ and $-z$ directions) was allowed to |
| 777 |
|
relax under ambient temperature and pressure. A separate (but |
| 778 |
|
identically sized) box of SPC/E water was also equilibrated at ambient |
| 779 |
|
conditions. The two boxes were combined by removing all water |
