small modifs

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Pierre-Francois Loos 2023-03-05 16:04:46 +01:00
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@ -303,7 +303,7 @@ where $\boldsymbol{\eta}(s)$, the flow generator, is defined as
\boldsymbol{\eta}(s) = \dv{\bU(s)}{s} \bU^\dag(s) = - \boldsymbol{\eta}^\dag(s). \boldsymbol{\eta}(s) = \dv{\bU(s)}{s} \bU^\dag(s) = - \boldsymbol{\eta}^\dag(s).
\end{equation} \end{equation}
\ant{The flow equation can be approximately solved by introduction of an approximate form of $\boldsymbol{\eta}(s)$.} The flow equation can be approximately solved by introducing an approximate form of $\boldsymbol{\eta}(s)$.
In this work, we consider Wegner's canonical generator \cite{Wegner_1994} In this work, we consider Wegner's canonical generator \cite{Wegner_1994}
\begin{equation} \begin{equation}
\boldsymbol{\eta}^\text{W}(s) = \comm{\bH^\text{d}(s)}{\bH(s)} = \comm{\bH^\text{d}(s)}{\bH^\text{od}(s)}, \boldsymbol{\eta}^\text{W}(s) = \comm{\bH^\text{d}(s)}{\bH(s)} = \comm{\bH^\text{d}(s)}{\bH^\text{od}(s)},
@ -338,7 +338,7 @@ Then, as performed in Sec.~\ref{sec:srggw}, one can collect order by order the t
\label{sec:srggw} \label{sec:srggw}
%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%%%%%%%%%%%%%%
\ant{Finally, the two previous subsections will be combined by applying the SRG method to the $GW$ formalism.} Here, we combine the concepts of the two previous subsections and apply the SRG method to the $GW$ formalism.
However, to do so, one must identify the coupling terms in Eq.~\eqref{eq:quasipart_eq}, which is not straightforward. However, to do so, one must identify the coupling terms in Eq.~\eqref{eq:quasipart_eq}, which is not straightforward.
A way around this problem is to transform Eq.~\eqref{eq:quasipart_eq} to an equivalent upfolded form which elegantly highlights the coupling terms. A way around this problem is to transform Eq.~\eqref{eq:quasipart_eq} to an equivalent upfolded form which elegantly highlights the coupling terms.
Indeed, the $GW$ quasiparticle equation is equivalent to the diagonalization of the following matrix \cite{Bintrim_2021,Tolle_2022} Indeed, the $GW$ quasiparticle equation is equivalent to the diagonalization of the following matrix \cite{Bintrim_2021,Tolle_2022}
@ -654,7 +654,7 @@ Note that, after this transformation, the form of the regularizer is actually cl
%=================================================================% %=================================================================%
% Reference comp det % Reference comp det
Our set of molecules is composed by closed-shell compounds that correspond to the 50 smallest (wrt the number of electrons) atoms and molecules of the $GW$100 benchmark set. \cite{vanSetten_2015} Our set of systems is composed by closed-shell compounds that correspond to the 50 smallest atoms and molecules (in terms of the number of electrons) of the $GW$100 benchmark set. \cite{vanSetten_2015}
Following the same philosophy as the \textsc{quest} database for neutral excited states, \cite{Loos_2020d,Veril_2021} their geometries have been optimized at the CC3 level (without frozen core) \cite{Christiansen_1995b,Koch_1997} in the aug-cc-pVTZ basis set using the \textsc{cfour} program. \cite{CFOUR} Following the same philosophy as the \textsc{quest} database for neutral excited states, \cite{Loos_2020d,Veril_2021} their geometries have been optimized at the CC3 level (without frozen core) \cite{Christiansen_1995b,Koch_1997} in the aug-cc-pVTZ basis set using the \textsc{cfour} program. \cite{CFOUR}
The reference CCSD(T) principal ionization potentials (IPs) and electron affinities (EAs) have been obtained using Gaussian 16 \cite{g16} with default parameters, that is, within the restricted and unrestriced HF formalism for the neutral and charged species, respectively. The reference CCSD(T) principal ionization potentials (IPs) and electron affinities (EAs) have been obtained using Gaussian 16 \cite{g16} with default parameters, that is, within the restricted and unrestriced HF formalism for the neutral and charged species, respectively.
@ -665,8 +665,8 @@ In all $GW$ calculations, we use the aug-cc-pVTZ cartesian basis set and self-co
We use (restricted) HF guess orbitals and energies for all self-consistent $GW$ calculations. We use (restricted) HF guess orbitals and energies for all self-consistent $GW$ calculations.
The maximum size of the DIIS space \cite{Pulay_1980,Pulay_1982} and the maximum number of iterations were set to 5 and 64, respectively. The maximum size of the DIIS space \cite{Pulay_1980,Pulay_1982} and the maximum number of iterations were set to 5 and 64, respectively.
In practice, one may achieve convergence, in some cases, by adjusting these parameters or by using an alternative mixing scheme. In practice, one may achieve convergence, in some cases, by adjusting these parameters or by using an alternative mixing scheme.
However, in order to perform a black-box comparison, these parameters have been fixed to these default values. However, in order to perform black-box comparisons, these parameters have been fixed to these default values.
\ant{The $\eta$ value has been set to \num{e-3} for the conventional $G_0W_0$ calculation while for (SRG-)qs$GW$ calculations the $\eta$ value has been chosen as the largest value where one successfully converges the 50 systems of the test set.} The $\eta$ value has been set to \num{e-3} for the conventional $G_0W_0$ calculations while, for the (SRG-)qs$GW$ calculations, $\eta$ has been chosen as the largest value where one successfully converges the 50 systems composing the test set.
%=================================================================% %=================================================================%
\section{Results} \section{Results}
@ -734,7 +734,6 @@ As soon as $s$ is large enough to decouple the 2h1p block, the IP starts decreas
In addition, the qs$GW$ and SRG-qs$GW$ methods based on a TDA screening (dubbed qs$GW^\TDA$ and SRG-qs$GW^\TDA$) are also considered in Fig.~\ref{fig:fig2}. In addition, the qs$GW$ and SRG-qs$GW$ methods based on a TDA screening (dubbed qs$GW^\TDA$ and SRG-qs$GW^\TDA$) are also considered in Fig.~\ref{fig:fig2}.
The TDA values are now underestimating the IP, unlike their RPA counterparts. The TDA values are now underestimating the IP, unlike their RPA counterparts.
For both static self-energies, the TDA leads to a slight increase in the absolute error. For both static self-energies, the TDA leads to a slight increase in the absolute error.
\trashant{This trend is investigated in more detail in the next subsection.}
Next, we investigate the flow parameter dependence of SRG-qs$GW$ for three more challenging molecular systems. Next, we investigate the flow parameter dependence of SRG-qs$GW$ for three more challenging molecular systems.
The left panel of Fig.~\ref{fig:fig3} shows the results for the lithium dimer, \ce{Li2}, which is an interesting case because, unlike in water, the HF approximation underestimates the reference IP. The left panel of Fig.~\ref{fig:fig3} shows the results for the lithium dimer, \ce{Li2}, which is an interesting case because, unlike in water, the HF approximation underestimates the reference IP.
@ -768,6 +767,7 @@ Therefore, it seems that the effect of the TDA cannot be systematically predicte
\includegraphics[width=\linewidth]{fig5.pdf} \includegraphics[width=\linewidth]{fig5.pdf}
\caption{ \caption{
Histogram of the errors (with respect to $\Delta$CCSD(T)) for the first ionization potential of the GW50 test set calculated using HF, $G_0W_0$@HF, qs$GW$ and SRG-qs$GW$. Histogram of the errors (with respect to $\Delta$CCSD(T)) for the first ionization potential of the GW50 test set calculated using HF, $G_0W_0$@HF, qs$GW$ and SRG-qs$GW$.
\PFL{Add MAE and MSE values to each figure.}
\label{fig:fig4}} \label{fig:fig4}}
\end{figure*} \end{figure*}
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@ -890,6 +890,7 @@ On the other hand, the imaginary shift regularizer acts equivalently on intruder
\includegraphics[width=\linewidth]{fig7.pdf} \includegraphics[width=\linewidth]{fig7.pdf}
\caption{ \caption{
Histogram of the errors (with respect to $\Delta$CCSD(T)) for the first electron attachment of the GW50 test set calculated using HF, $G_0W_0$@HF, qs$GW$ and SRG-qs$GW$. Histogram of the errors (with respect to $\Delta$CCSD(T)) for the first electron attachment of the GW50 test set calculated using HF, $G_0W_0$@HF, qs$GW$ and SRG-qs$GW$.
\PFL{Add MAE and MSE values to each figure.}
\label{fig:fig6}} \label{fig:fig6}}
\end{figure*} \end{figure*}
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