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amsmath,amssymb, |
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jcp]{revtex4-1} |
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\usepackage[version=3]{mhchem} % this is a great package for formatting chemical reactions |
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\usepackage{url} |
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\usepackage{rotating} |
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%\usepackage[mathlines]{lineno}% Enable numbering of text and display math |
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%\linenumbers\relax % Commence numbering lines |
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|
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sphere. There are also significant modifications made to make the |
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forces and torques go smoothly to zero at the cutoff distance. |
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|
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\begin{figure} |
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\includegraphics[width=3in]{SM} |
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\caption{Reversed multipoles are projected onto the surface of the |
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cutoff sphere. The forces, torques, and potential are then smoothly |
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shifted to zero as the sites leave the cutoff region.} |
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\label{fig:shiftedMultipoles} |
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\end{figure} |
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|
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As in the point-charge approach, there is an additional contribution |
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from self-neutralization of site $i$. The self term for multipoles is |
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constant), $N$ is the number of dipoles per unit volume, and $\mu$ is |
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the strength of the dipole. Energy constants (converged to 1 part in |
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|
$10^9$) are given in the supplemental information. |
1413 |
– |
\begin{figure}[!htbp] |
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|
1422 |
< |
\includegraphics[width=3.5in]{Dipoles_rcutConvergence-crop.pdf} |
1423 |
< |
|
1424 |
< |
\includegraphics[width=3.5in]{Quadrupoles_rcutConvergence-crop.pdf} |
1425 |
< |
\caption{Convergence to the analytic energy constants as a function of |
1426 |
< |
cutoff radius (normalized by the lattice constant) for the different |
1427 |
< |
real-space methods for (a) dipolar and (b) quadrupolar crystals.The energy constants for hard, SP, GSF, TSF and analytic methods are represented by black sold-circle, red solid-square,green solid-diamond and grey dashed line respectively. |
1428 |
< |
The left panel shows results for the undamped kernel ($1/r$), while the damped |
1429 |
< |
error function kernel, $B_0(r)$ was used in the right panel. } |
1430 |
< |
\label{fig:Dipoles_rcutCovergence-crop.pdf} |
1431 |
< |
\label{fig:QuadrupolesrcutCovergence-crop.pdf} |
1422 |
> |
\begin{figure} |
1423 |
> |
\includegraphics[width=\linewidth]{Dipoles_rCutNew.pdf} |
1424 |
> |
\caption{Convergence of the lattice energy constants as a function of |
1425 |
> |
cutoff radius (normalized by the lattice constant, $a$) for the new |
1426 |
> |
real-space methods. Three dipolar crystal structures were sampled, |
1427 |
> |
and the analytic energy constants for the three lattices are |
1428 |
> |
indicated with grey dashed lines. The left panel shows results for |
1429 |
> |
the undamped kernel ($1/r$), while the damped error function kernel, |
1430 |
> |
$B_0(r)$ was used in the right panel.} |
1431 |
> |
\label{fig:Dipoles_rCut} |
1432 |
|
\end{figure} |
1433 |
+ |
|
1434 |
+ |
\begin{figure} |
1435 |
+ |
\includegraphics[width=\linewidth]{Dipoles_alphaNew.pdf} |
1436 |
+ |
\caption{Convergence to the lattice energy constants as a function of |
1437 |
+ |
the reduced damping parameter ($\alpha^* = \alpha a$) for the |
1438 |
+ |
different real-space methods in the same three dipolar crystals in |
1439 |
+ |
Figure \ref{fig:Dipoles_rCut}. The left panel shows results for a |
1440 |
+ |
relatively small cutoff radius ($r_c = 4.5 a$) while a larger cutoff |
1441 |
+ |
radius ($r_c = 6 a$) was used in the right panel. } |
1442 |
+ |
\label{fig:Dipoles_alpha} |
1443 |
+ |
\end{figure} |
1444 |
+ |
|
1445 |
|
For the purposes of testing the energy expressions and the |
1446 |
|
self-neutralization schemes, the primary quantity of interest is the |
1447 |
|
analytic energy constant for the perfect arrays. Convergence to these |
1448 |
|
constants are shown as a function of both the cutoff radius, $r_c$, |
1449 |
< |
and the damping parameter, $\alpha$ in Figs. |
1450 |
< |
\ref{fig:energyConstVsCutoff} and XXX. We have simultaneously tested a |
1451 |
< |
hard cutoff (where the kernel is simply truncated at the cutoff |
1452 |
< |
radius), as well as a shifted potential (SP) form which includes a |
1449 |
> |
and the damping parameter, $\alpha$ in Figs. \ref{fig:Dipoles_rCut} |
1450 |
> |
and \ref{fig:Dipoles_alpha}. We have simultaneously tested a hard |
1451 |
> |
cutoff (where the kernel is simply truncated at the cutoff radius), as |
1452 |
> |
well as a shifted potential (SP) form which includes a |
1453 |
|
potential-shifting and self-interaction term, but does not shift the |
1454 |
|
forces and torques smoothly at the cutoff radius. The SP method is |
1455 |
|
essentially an extension of the original Wolf method for multipoles. |
1437 |
– |
\begin{figure}[!htbp] |
1456 |
|
|
1439 |
– |
\includegraphics[width=3.5in]{Dipoles_alphaConvergence-crop.pdf} |
1440 |
– |
|
1441 |
– |
\includegraphics[width=3.5in]{Quadrupoles_alphaConvergence-crop.pdf} |
1442 |
– |
\caption{Convergence to the analytic energy constants as a function of |
1443 |
– |
cutoff damping alpha for the different |
1444 |
– |
real-space methods for (a) dipolar and (b) quadrupolar crystals.The energy constants for hard, SP, GSF, TSF, and analytic methods are represented by the black sold-circle, red solid-square, green solid-diamond, and grey dashed line respectively. |
1445 |
– |
The left panel shows results for the undamped kernel ($1/r$), while the damped |
1446 |
– |
error function kernel, $B_0(r)$ was used in the right panel. } |
1447 |
– |
\label{fig:Dipoles_alphaCovergence-crop.pdf} |
1448 |
– |
\label{fig:Quadrupoles_alphaCovergence-crop.pdf} |
1449 |
– |
\end{figure} |
1457 |
|
The Hard cutoff exhibits oscillations around the analytic energy |
1458 |
|
constants, and converges to incorrect energies when the complementary |
1459 |
|
error function damping kernel is used. The shifted potential (SP) and |
1484 |
|
(For the traceless quadrupole tensor, $\Theta = 3 Q - \text{Tr} Q$, |
1485 |
|
the effective moment, $\bar{Q}^2 = \frac{2}{3} \Theta : \Theta$.) |
1486 |
|
|
1487 |
+ |
\begin{figure} |
1488 |
+ |
\includegraphics[width=\linewidth]{Quadrupoles_rcutConvergence-crop.pdf} |
1489 |
+ |
\caption{Convergence to the analytic energy constants as a function of |
1490 |
+ |
cutoff radius (normalized by the lattice constant) for the different |
1491 |
+ |
real-space methods for (a) dipolar and (b) quadrupolar crystals.The energy constants for hard, SP, GSF, TSF and analytic methods are represented by black sold-circle, red solid-square,green solid-diamond and grey dashed line respectively. |
1492 |
+ |
The left panel shows results for the undamped kernel ($1/r$), while the damped |
1493 |
+ |
error function kernel, $B_0(r)$ was used in the right panel. } |
1494 |
+ |
\label{fig:QuadrupolesrcutCovergence-crop.pdf} |
1495 |
+ |
\end{figure} |
1496 |
+ |
|
1497 |
+ |
|
1498 |
+ |
\begin{figure}[!htbp] |
1499 |
+ |
\includegraphics[width=3.5in]{Quadrupoles_alphaConvergence-crop.pdf} |
1500 |
+ |
\caption{Convergence to the analytic energy constants as a function of |
1501 |
+ |
cutoff damping alpha for the different |
1502 |
+ |
real-space methods for (a) dipolar and (b) quadrupolar crystals.The energy constants for hard, SP, GSF, TSF, and analytic methods are represented by the black sold-circle, red solid-square, green solid-diamond, and grey dashed line respectively. |
1503 |
+ |
The left panel shows results for the undamped kernel ($1/r$), while the damped |
1504 |
+ |
error function kernel, $B_0(r)$ was used in the right panel. } |
1505 |
+ |
\label{fig:Quadrupoles_alphaCovergence-crop.pdf} |
1506 |
+ |
\end{figure} |
1507 |
+ |
|
1508 |
+ |
|
1509 |
|
\section{Conclusion} |
1510 |
|
We have presented two efficient real-space methods for computing the |
1511 |
|
interactions between point multipoles. These methods have the benefit |
1534 |
|
\begin{acknowledgments} |
1535 |
|
JDG acknowledges helpful discussions with Christopher |
1536 |
|
Fennell. Support for this project was provided by the National |
1537 |
< |
Science Foundation under grant CHE-0848243. Computational time was |
1537 |
> |
Science Foundation under grant CHE-1362211. Computational time was |
1538 |
|
provided by the Center for Research Computing (CRC) at the |
1539 |
|
University of Notre Dame. |
1540 |
|
\end{acknowledgments} |
1707 |
|
``Bare Coulomb.'' Equations \ref{eq:b9} to \ref{eq:b13} are still |
1708 |
|
correct for GSF electrostatics if the subscript $n$ is eliminated. |
1709 |
|
|
1710 |
+ |
\newpage |
1711 |
+ |
|
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|
\bibliography{multipole} |
1713 |
|
|
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|
\end{document} |