working on the theory section

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@ -2,4 +2,6 @@
\BOOKMARK [1][-]{section*.1}{Abstract}{section*.2}% 1
\BOOKMARK [1][-]{section*.3}{Introduction}{section*.2}% 3
\BOOKMARK [1][-]{section*.4}{Theory}{section*.2}% 4
\BOOKMARK [1][-]{section*.5}{Results}{section*.2}% 5
\BOOKMARK [2][-]{section*.5}{Basic formal equations}{section*.4}% 5
\BOOKMARK [2][-]{section*.6}{Definition of an effective interaction within B}{section*.4}% 6
\BOOKMARK [1][-]{section*.7}{Results}{section*.2}% 7

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@ -62,6 +62,7 @@
\newcommand{\efcicomplete}[0]{E_{\text{FCI}}^{\infty}}
\newcommand{\ecccomplete}[0]{E_{\text{CCSD(T)}}^{\infty}}
\newcommand{\ecc}[0]{E_{\text{CCSD(T)}}^{\Bas}}
\newcommand{\efuncbasisFCI}[0]{\bar{E}^\Bas[\denFCI]}
\newcommand{\efuncbasisfci}[0]{\bar{E}^\Bas[\denfci]}
\newcommand{\efuncbasis}[0]{\bar{E}^\Bas[\den]}
\newcommand{\efuncden}[1]{\bar{E}^\Bas[#1]}
@ -85,8 +86,7 @@
% numbers
\newcommand{\rnum}[0]{{\rm I\!R}}
\newcommand{\bfr}[1]{{\bf x}_{#1}}
\newcommand{\bfrb}[1]{{\bf r}_{#1}}
\newcommand{\bfr}[1]{{\bf r}_{#1}}
\newcommand{\dr}[1]{\text{d}\bfr{#1}}
\newcommand{\rr}[2]{\bfr{#1}, \bfr{#2}}
\newcommand{\rrrr}[4]{\bfr{#1}, \bfr{#2},\bfr{#3},\bfr{#4} }
@ -109,9 +109,9 @@
\newcommand{\fbasis}[0]{f_{\wf{}{\Bas}}(\bfr{1},\bfr{2})}
\newcommand{\fbasisval}[0]{f_{\wf{}{\Bas}}^{\text{val}}(\bfr{1},\bfr{2})}
\newcommand{\ontop}[2]{ n^{(2)}_{#1}({\bf #2}_1)}
\newcommand{\twodmrpsi}[0]{ n^{(2)}_{\wf{}{\Bas}}(\rrrr{1}{2}{2}{1})}
\newcommand{\twodmrdiagpsi}[0]{ n^{(2)}_{\wf{}{\Bas}}(\rr{1}{2})}
\newcommand{\twodmrdiagpsival}[0]{ n^{(2)}_{\wf{}{\Bas},\,\text{val}}(\rr{1}{2})}
\newcommand{\twodmrpsi}[0]{ n^{2}_{\wf{}{\Bas}}(\rrrr{1}{2}{2}{1})}
\newcommand{\twodmrdiagpsi}[0]{ n^{2}_{\wf{}{\Bas}}(\rr{1}{2})}
\newcommand{\twodmrdiagpsival}[0]{ n^{2}_{\wf{}{\Bas},\,\text{val}}(\rr{1}{2})}
\newcommand{\gammamnpq}[1]{\Gamma_{mn}^{pq}[#1]}
\newcommand{\gammamnkl}[0]{\Gamma_{mn}^{kl}}
\newcommand{\gammaklmn}[1]{\Gamma_{kl}^{mn}[#1]}
@ -133,6 +133,7 @@
\newcommand{\denmodel}[0]{\den_{\model}^\Bas}
\newcommand{\denmodelr}[0]{\den_{\model}^\Bas ({\bf r})}
\newcommand{\denfci}[0]{\den_{\psifci}}
\newcommand{\denFCI}[0]{\den^{\Bas}_{\text{FCI}}}
\newcommand{\denhf}[0]{\den_{\text{HF}}^\Bas}
\newcommand{\denrfci}[0]{\denr_{\psifci}}
\newcommand{\dencipsir}[0]{{n}_{\text{CIPSI}}^\Bas({\bf r})}
@ -188,6 +189,7 @@
\newcommand{\modY}{\text{Y}}
% basis sets
\newcommand{\setdenbasis}{\mathcal{N}_{\Bas}}
\newcommand{\Bas}{\mathcal{B}}
\newcommand{\Basval}{\mathcal{B}_\text{val}}
\newcommand{\Val}{\mathcal{V}}
@ -200,10 +202,9 @@
\newcommand{\Gam}[2]{\Gamma_{#1}^{#2}}
% coordinates
\newcommand{\br}[1]{\mathbf{r}_{#1}}
\newcommand{\br}[1]{{\mathbf{r}_{#1}}}
\newcommand{\bx}[1]{\mathbf{x}_{#1}}
\newcommand{\dbr}[1]{d\br{#1}}
\newcommand{\dbx}[1]{d\bx{#1}}
\newcommand{\LCPQ}{Laboratoire de Chimie et Physique Quantiques (UMR 5626), Universit\'e de Toulouse, CNRS, UPS, France}
\newcommand{\LCT}{Laboratoire de Chimie Th\'eorique, Universit\'e Pierre et Marie Curie, Sorbonne Universit\'e, CNRS, Paris, France}
@ -273,7 +274,60 @@ When the molecular system
%%%%%%%%%%%%%%%%%%%%%%%%
The theoretical framework of the basis set correction have been derived in details in \cite{GinPraFerAssSavTou-JCP-18}, so we recall briefly the main equations involved for the present study.
\subsection{Basic formal equations}
The exact ground state energy $E_0$ of a $N-$electron system can be obtained by the Levy-Lieb constrained search formalism which is an elegant mathematical framework connecting WFT and DFT
\begin{equation}
\label{eq:levy}
E_0 = \min_{\denr} \bigg\{ F[\denr] + (v_{\text{ne}} (\br{}) |\denr) \bigg\},
\end{equation}
where $(v_{ne}(\br)|\denr)$ is the nuclei-electron interaction for a given density $\denr$ and $F[\denr]$ is the so-called Levy-Liev universal density functional
\begin{equation}
\label{eq:levy_func}
F[\denr] = \min_{\Psi \rightarrow \denr} \elemm{\Psi}{\kinop +\weeop }{\Psi}.
\end{equation}
The minimizing density $n_0$ of equation \eqref{eq:levy} is the exact ground state density.
As in practical calculations the minimization is performed over the set $\setdenbasis$ which are the densities representable in a basis set $\Bas$, we assume from thereon that the densities used in the equations belong to $\setdenbasis$.
Following equation (7) of \cite{GinPraFerAssSavTou-JCP-18}, we split $F[\denr]$ as
\begin{equation}
F[\denr] = \min_{\wf{}{\Bas} \rightarrow \denr} \elemm{\wf{}{\Bas}}{\kinop +\weeop}{\wf{}{\Bas}} + \efuncden{\denr}
\end{equation}
where $\efuncden{\denr}$ is the density functional complementary to the basis set $\Bas$ defined as
\begin{equation}
\begin{aligned}
\efuncden{\denr} =& \min_{\Psi \rightarrow \denr} \elemm{\Psi}{\kinop +\weeop }{\Psi} \\ 
&- \min_{\Psi^{\Bas} \rightarrow \denr} \elemm{\wf{}{\Bas}}{\kinop +\weeop}{\wf{}{\Bas}},
\end{aligned}
\end{equation}
and $\wf{}{\Bas}$ refer to $N-$electron wave functions expanded in $\Bas$.
The functional $\efuncden{\denr}$ must therefore recover all physical effects not included in the basis set $\Bas$.
Assuming that the FCI density $\denFCI$ in $\Bas$ is a good approximation of the exact density (see equations 12-15 of \cite{GinPraFerAssSavTou-JCP-18}), one obtains the following approximation for the exact ground state density
\begin{equation}
\label{eq:e0approx}
E_0 = \efci + \efuncbasisFCI
\end{equation}
where $\efci$ is the ground state FCI energy within $\Bas$. As it was originally shown in \cite{GinPraFerAssSavTou-JCP-18} and further emphasized in \cite{G2,excited}, the main role of $\efuncbasisFCI$ is to correct for the basis set incompleteness errors, a large part of which originates from the lack of cusp in any wave function developed in an incomplete basis set.
The whole purpose of this paper is to determine approximations for $\efuncbasisFCI$ which are suited for treating strong correlation regimes. The two requirement for such conditions are that i) it can be defined for multi-reference wave functions, ii) it must provide size extensive energies, iii) it is invariant of the $S_z$ component of a given spin multiplicity.
\subsection{Definition of an effective interaction within $\Bas$}
As it was originally shown by Kato\cite{kato}, the cusp in the exact wave function originates from the divergence of the coulomb interaction at the coalescence point. Therefore, the lack of cusp in any wave function $\wf{}{\Bas}$ could also originate from an effective non-divergent electron-electron interaction. In other words, the incompleteness of a finite basis set can be understood as the removal of the divergence at the electron coalescence point.
As it was originally derived in \cite{GinPraFerAssSavTou-JCP-18} (see section D and annexes), one can obtain an effective non divergent interaction, here referred as $\wbasis$, which reproduces the expectation value of the coulomb operator over a given wave function $\wf{}{\Bas}$. As we are interested in the behaviour at the coalescence point, we focus on the opposite spin part of the electron-electron interaction.
More specifically, we define the effective interaction associated to a given wave function $\wf{}{\Bas}$ as
\begin{equation}
\wbasis = \fbasis/\twodmrdiagpsi
\end{equation}
where $\twodmrdiagpsi$ is the opposite spin two-body density associated to $\wf{}{\Bas}$
\begin{equation}
\twodmrdiagpsi = \sum_{pqrs} \phi_{p}(\br) \phi_{q}(\br) \Gam{pq}{rs} \phi_{r}(\br) \phi_{s}(\br),
\end{equation}
$\Gam{pq}{rs}$
\begin{equation}
\int \int \dr{1} \dr{2} \wbasis \twodmrdiagpsi = \elemm{\wf{}{\Bas}}{\weeop}{\wf{}{\Bas}},
\end{equation}
where $\twodmrdiagpsi$ is the two-body density of
%%%%%%%%%%%%%%%%%%%%%%%%
\section{Results}
%%%%%%%%%%%%%%%%%%%%%%%%
@ -338,6 +392,16 @@ The theoretical framework of the basis set correction have been derived in detai
\end{figure}
\begin{figure}
\includegraphics[width=\linewidth]{data/H10/DFT_vqzE_relat_zoom.eps}\\
\includegraphics[width=\linewidth]{data/H10/DFT_vqzE_error.eps}\\
% \includegraphics[width=\linewidth]{fig2c}
\caption{
H$_{10}$, cc-pvqz: Comparison between the near FCI and corrected near FCI energies and the estimated exact one.
\label{fig:H10_vqz}}
\end{figure}