work done on algorithm

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Pierre-Francois Loos 2020-08-08 08:34:15 +02:00
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@ -1,13 +1,44 @@
%% This BibTeX bibliography file was created using BibDesk.
%% http://bibdesk.sourceforge.net/
%% Created for Pierre-Francois Loos at 2020-08-07 20:17:07 +0200
%% Created for Pierre-Francois Loos at 2020-08-08 08:15:47 +0200
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@article{Pulay_1980,
Author = {Pulay, P{\'e}ter},
Date-Added = {2020-08-08 08:15:42 +0200},
Date-Modified = {2020-08-08 08:15:42 +0200},
Doi = {10.1016/0009-2614(80)80396-4},
Issn = {00092614},
Journal = {Chem. Phys. Lett.},
Language = {en},
Month = jul,
Number = {2},
Pages = {393--398},
Title = {Convergence Acceleration of Iterative Sequences. the Case of Scf Iteration},
Volume = {73},
Year = {1980},
Bdsk-Url-1 = {https://dx.doi.org/10.1016/0009-2614(80)80396-4}}
@article{Pulay_1982,
Author = {Pulay, P.},
Date-Added = {2020-08-08 08:15:42 +0200},
Date-Modified = {2020-08-08 08:15:42 +0200},
Doi = {10.1002/jcc.540030413},
Issn = {0192-8651, 1096-987X},
Journal = {J. Comput. Chem.},
Language = {en},
Number = {4},
Pages = {556--560},
Title = {{{ImprovedSCF}} Convergence Acceleration},
Volume = {3},
Year = {1982},
Bdsk-Url-1 = {https://dx.doi.org/10.1002/jcc.540030413}}
@article{Assaraf_2000,
Author = {Assaraf, Roland and Caffarel, Michel and Khelif, Anatole},
Date-Added = {2020-08-07 20:12:45 +0200},

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@ -334,7 +334,10 @@ the FCI wave function.
\centering
\includegraphics[width=0.7\linewidth]{algorithm.pdf}
\caption{Algorithm showing the generation of the RS-DFT wave
function $\Psi^{\mu}$ starting from the .}
function $\Psi^{\mu}$ starting from $\Psi^{(0)}$.
The outer (macro-iteration) and inner (micro-iteration) loops are represented in red and blue, respectively.
The steps common to both loops are represented in purple.
DIIS extrapolations of the one-electron density are introduced in both the outer and inner loops in order to speed up convergence of the self-consistent process.}
\label{fig:algo}
\end{figure*}
@ -347,23 +350,28 @@ connecting HF to FCI which consists in increasing the number of determinants.
We follow the KS-to-FCI path by performing FCI calculations using the
RS-DFT Hamiltonian with different values of $\mu$.
Our algorithm, depicted in Fig.~\ref{fig:algo}, starts with a
single- and multi-determinant wave function $\Psi^{(0)}$.
single- or multi-determinant wave function $\Psi^{(0)}$ which can
be obtained in many different ways depending on the system that one considers.
One of the particularity of the present work is that we
have used the CIPSI algorithm to perform approximate FCI calculations
with the RS-DFT Hamiltonians $\hat{H}^\mu$. \cite{GinPraFerAssSavTou-JCP-18}
In the outer loop (red), a CIPSI selection is performed with a RS Hamiltonian
parameterized using the current one-electron density.
An inner loop (blue) is introduced to accelerate the
use the CIPSI algorithm to perform approximate FCI calculations
with the RS-DFT Hamiltonian $\hat{H}^\mu$. \cite{GinPraFerAssSavTou-JCP-18}
This provides a multi-determinant trial wave function $\Psi^{\mu}$ that one can ``feed'' to DMC.
In the outer (macro-iteration) loop (red), at the $k$th iteration, a CIPSI selection is performed
to obtain $\Psi^{\mu\,(k)}$ with the RS Hamiltonian $\hat{H}^{\mu\,(k)}$
parameterized using the current one-electron density $n^{(k)}$.
At each iteration, the number of determinants in $\Psi^{\mu\,(k)}$ increases.
One exits the macro-iteration loop when the absolute energy difference between two successive iterations $\Delta E^{(k)}$ is below a threshold $\tau_1$ that has been set to \titou{???} in the present study.
An inner (micro-iteration) loop (blue) is introduced to accelerate the
convergence of the self-consistent calculation, in which the set of
determinants is kept fixed, and only the diagonalization of the
RS-Hamiltonian is performed iteratively with the updated density.
determinants in $\Psi^{\mu\,(k,l)}$ is kept fixed, and only the diagonalization of
$\hat{H}^{\mu\,(k,l)}$ is performed iteratively with the updated density $n^{(k,l)}$.
The micro-iteration loop is exited when the absolute energy difference between two successive iterations $\Delta E^{(k,l)}$ is below a threshold $\tau_2$ that has been set to \titou{???} in the present study.
The convergence of the algorithm was further improved
by introducing a direct inversion in the iterative subspace (DIIS)
step to extrapolate the density both in the outer and inner loops.
step to extrapolate the density both in the outer and inner loops. \cite{Pulay_1980,Pulay_1982}
Note that any range-separated post-HF method can be
implemented using this scheme by just replacing the CIPSI step by the
post-HF method of interest.
\titou{T2: introduce $\tau_1$ and $\tau_2$. More description of the algorithm needed.}
Note that, thanks to the self-consistent nature of the algorithm,
the final trial wave function $\Psi^{\mu}$ is independent of the starting wave function $\Psi^{(0)}$.