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@ -133,25 +133,24 @@ In physics perturbation theory is often a good way to improve the obtained resul
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\begin{beamerboxesrounded}[scheme=foncé]{\centering The Fock operator}
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\begin{equation}
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F = T + J + K
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F = \sum\limits_{i=1}^{n} f(i) \hspace{0.3cm} ; \hspace{0.3cm} f(i) = h(i) + \sum\limits_{i=1}^{n/2} \left[2J_j(i) - K_j(i)\right]
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\end{equation}
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\end{beamerboxesrounded}
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\begin{itemize}
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\centering
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\item $T$: Kinetic energy operator
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\item $J$: Coulomb operator
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\item $K$: Exchange operator
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\item $f(i)$: Fock operator
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\item $h(i)$: One electron Hamiltonian
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\item $J_j(i)$: Coulomb operator
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\item $K_j(i)$: Exchange operator
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\end{itemize}
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\pause[3]
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\begin{beamerboxesrounded}[scheme=foncé]{}
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\centering
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Full Configuration Interaction gives access to high-order terms of the perturbation series!
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Full Configuration Interaction gives access to high-order terms of the perturbation series !
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\end{beamerboxesrounded}
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\end{frame}
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@ -160,9 +159,7 @@ Full Configuration Interaction gives access to high-order terms of the perturbat
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\begin{figure}
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\centering
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\includegraphics[width=0.45\textwidth]{gill1986.png}
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\caption{\centering Barriers to homolytic fission of \ce{He2^2+} at MPn/STO-3G level ($n = 1$--$20$).}
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\label{fig:my_label}
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\end{figure}
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@ -186,7 +183,6 @@ Full Configuration Interaction gives access to high-order terms of the perturbat
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\caption{\centering Percentage of electron correlation energy recovered and $\expval{S^2}$ for the \ce{H2} molecule as a function of bond length (r,\si{\angstrom}) in the STO-3G basis set.}
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\label{tab:my_label}
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\end{table}
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\end{frame}
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@ -355,12 +351,28 @@ The \textcolor{red}{radius of convergence} of the Taylor expansion of a function
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\end{frame}
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\begin{frame}{The Møller-Plesset Hamiltonian}
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\begin{equation}
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H(\lambda)=H_0 + \lambda (H_\text{phys} - H_0)
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\end{equation}
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\begin{equation}
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H_\text{phys}=\sum\limits_{j=1}^{n}\left[ -\frac{1}{2}\grad_j^2 - \sum\limits_{k=1}^{N} \frac{Z_k}{|\vb{r}_j-\vb{R}_k|}+\sum\limits_{j<l}^{n}\frac{1}{|\vb{r}_j-\vb{r}_l|}\right]
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\end{equation}
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\begin{equation}
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H_0=\sum\limits_{j=1}^{n}\left[ -\frac{1}{2}\grad_j^2 - \sum\limits_{k=1}^{N} \frac{Z_k}{|\vb{r}_j-\vb{R}_k|}+V_j^{(scf)}\right]
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\end{equation}
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\end{frame}
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\begin{frame}{Existence of a critical point\footcite{stillinger_mollerplesset_2000}}
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For $\lambda<0$:
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\begin{equation*}
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H(\lambda)=\sum\limits_{j=1}^{2n}\left[ \underbrace{-\frac{1}{2}\grad_j^2 - \sum\limits_{k=1}^{N} \frac{Z_k}{|\vb{r}_j-\vb{R}_k|}}_{\text{Independant of }\lambda} + \overbrace{(1-\lambda)V_j^{(scf)}}^{\textcolor{red}{Repulsive}}+\underbrace{\lambda\sum\limits_{j<l}^{2n}\frac{1}{|\vb{r}_j-\vb{r}_l|}}_{\textcolor{blue}{Attractive}} \right]
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H(\lambda)=\sum\limits_{j=1}^{n}\left[ \underbrace{-\frac{1}{2}\grad_j^2 - \sum\limits_{k=1}^{N} \frac{Z_k}{|\vb{r}_j-\vb{R}_k|}}_{\text{Independant of }\lambda} + \overbrace{(1-\lambda)V_j^{(scf)}}^{\textcolor{red}{Repulsive}}+\underbrace{\lambda\sum\limits_{j<l}^{n}\frac{1}{|\vb{r}_j-\vb{r}_l|}}_{\textcolor{blue}{Attractive}} \right]
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\end{equation*}
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\end{frame}
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@ -441,71 +453,7 @@ Proof of the existence of this group of sharp avoided crossings for Ne, He and H
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\end{frame}
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\section{The spherium model}
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\begin{frame}{Spherium: a theoretical playground\footcite{loos_ground_2009}}
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\begin{beamerboxesrounded}[scheme=foncé]{\centering Two electrons on a sphere Hamiltonian}
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\begin{equation*}
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H=-\frac{1}{2}(\grad_1^2 + \grad_2^2) + \frac{1}{r_{12}}
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\end{equation*}
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\end{beamerboxesrounded}
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\vspace{0.5cm}
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\begin{columns}
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\column{0.48\textwidth}
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\centering{Small $R$}
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\vspace{0.5cm}
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\begin{itemize}
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\item $E_\text{kin} \gg E_\text{pot}$
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\item Uniform density of electrons
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\item \textcolor{red}{Weak correlation}
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\end{itemize}
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\vspace{0.5cm}
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\column{0.48\textwidth}
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\centering{Large $R$}
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\vspace{0.5cm}
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\begin{itemize}
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\item $E_\text{kin} \ll E_\text{pot}$
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\item Electrons on the opposite sides of the sphere
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\item \textcolor{red}{Strong correlation}
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\end{itemize}
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\end{columns}
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\end{frame}
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\begin{frame}{Apparition of a class $\beta$ singularity}
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\pause[1]
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\begin{beamerboxesrounded}[scheme=foncé]{\centering Expectation}
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The electrons are restricted to the surface of the sphere so we should not observe singularities characteristic of ionization processes.
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\end{beamerboxesrounded}
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\vspace{0.5cm}
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\pause[2]
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\large But for some values of R... we actually observe some $\beta$ singularities!
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\centering Why?
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\vspace{0.5cm}
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\pause[3]
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\begin{beamerboxesrounded}[scheme=foncé]{\centering Symmetry breaking}
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The $\beta$ singularities observed are connected to the symmetry breaking of the wave function.
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\end{beamerboxesrounded}
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\end{frame}
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\section{Conclusion}
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\begin{frame}{Conclusion}
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@ -515,20 +463,14 @@ The $\beta$ singularities observed are connected to the symmetry breaking of the
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By understanding how the singularities are localized in the complex plane we hope that it will gives us a deep understanding of the strengths and weaknesses of the Møller-Plesset method to get the correlation energy.
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\end{beamerboxesrounded}
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\vspace{0.5cm}
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\pause[2]
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\vspace{0.5cm}
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But there is an other secret application of exceptional points...
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\pause[3]
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\vspace{0.5cm}
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\begin{beamerboxesrounded}[scheme=foncé]{\centering A new way to excited states energies}
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The exceptionnal points connect ground and excited states in the complex plane. Using those properties one can smoothly morph a ground state in an excited state.
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\begin{beamerboxesrounded}[scheme=foncé]{\centering Spherium: a theoretical playground}
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We will use the spherium model (two opposite-spin electrons restricted to remain on a surface of a sphere of radius $R$) to investigate the effects of symmetry breaking on singularities.
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\end{beamerboxesrounded}
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\end{frame}
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\end{document}
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\end{document}
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