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update the spline SPO description in the manual. 

git-svn-id: https://subversion.assembla.com/svn/qmcdev/trunk@6908 e5b18d87-469d-4833-9cc0-8cdfa06e9491
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Ye Luo 2016-05-16 22:45:09 +00:00
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13
manual/bibliography.bib
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@ -135,6 +135,17 @@ author = "Vincent Natoli and David M. Ceperley"
url = {http://link.aps.org/doi/10.1103/PhysRevLett.97.076404}
}
@article{blips4QMC,
title = {{An efficient localized basis set for quantum Monte Carlo calculations on condensed matter}},
author = {Alf{\`{e}}, D. and Gillan, M. J.},
journal={Physical Review B},
volume = {70},
number = {16},
pages = {161101},
year = {2004},
publisher={APS}
}
@article{Krogel2016nexus,
title = "Nexus: A modular workflow management system for quantum simulation codes ",
journal = "Computer Physics Communications ",
@ -155,4 +166,4 @@ keywords = "Density functional theory",
keywords = "QMCPACK",
keywords = "Quantum Espresso",
keywords = "VASP "
}
}

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manual/qmcpack_manual.pdf
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15
manual/spo_spline.tex
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@ -8,7 +8,7 @@ In principle, PW basis set can be used to express SPOs directly in QMC like in D
but it introduces an unfavorable scaling due to the fact
that the basis set size increases linearly as the system size.
For this reason, it is efficient to use a localized basis with compact
support and a good transferability from pale wave basis.
support and a good transferability from plane wave basis.
In particular, 3D tricubic B-splines provide a basis in which only
64 elements are nonzero at any given point in space~\cite{blips4QMC}.
@ -40,7 +40,7 @@ the expense of increased memory use, which is easily overcome by the large
aggregate memory available per node through OpenMP/MPI hybrid QMC.
The input xml block for the spline SPOs is give in Listing~\ref{listing:splineSPOs}. A list of options is given in
Table~\ref{table:splineSPOs}. \texttt{QMCPACK} has a very useful option \texttt{--save\_wfs} which allows to dump
Table~\ref{table:splineSPOs}. \texttt{QMCPACK} has a very useful command line option \texttt{--save\_wfs} which allows to dump
the real space B-spline coefficient table into a h5 file on the disk.
When the orbital transformation from k space to B-spline requires more than available amount of scratch memory on the compute nodes,
users can perform this step on fat nodes and transfer back the h5 file for QMC calculations.
@ -59,8 +59,8 @@ users can perform this step on fat nodes and transfer back the h5 file for QMC c
& \texttt{href} & text & & & Path to the h5 file generated by pw2qmcpack.x. \\
& \texttt{tilematrix} & 9 integers & & & Tiling matrix used to expand supercell. \\
& \texttt{twistnum} & integer & & & Index of the super twist. \\
& \texttt{twist} & 3 integers & & & Super twist. \\
& \texttt{meshfactor} & float & & & Grid spacing with respect to the original one calculated from h5. \\
& \texttt{twist} & 3 floats & & & Super twist. \\
& \texttt{meshfactor} & float & $\le 1.0$ & & Grid spacing ratio. \\
& \texttt{precision} & text & single/double & & Precision of spline coefficients. \\
& \texttt{gpu} & text & yes/no & & GPU switch. \\
& \texttt{source} & text & \textit{any} & ion0 & Particle set with the position of atom centers. \\
@ -101,5 +101,10 @@ users can perform this step on fat nodes and transfer back the h5 file for QMC c
</determinantset>
\end{lstlisting}
Additional information:
\begin{itemize}
\item \texttt{precision}. Using single precision not only saves memory usage but also speeds up the B-spline evaluation. It is recommended to use single precision since we saw little chance of really compromising the accuracy of calculation.
\item \texttt{meshfactor}. It is the ratio of actual grid spacing of B-splines used in QMC calculation with respect to the original one calculated from h5. Smaller meshfactor saves memory usage but reduces accuracy. The effects are similar to reducing plane wave cutoff in DFT calculation. Use with caution!
\item \texttt{twistnum}. If positive, it is the index. It is recommended not to take this way since the indexing may show some uncertainty. If negative, the super twist is referred by \texttt{twist}.
\end{itemize}
\label{sec:splinebasis}