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@ -133,25 +133,24 @@ In physics perturbation theory is often a good way to improve the obtained resul
\begin{beamerboxesrounded}[scheme=foncé]{\centering The Fock operator}
\begin{equation}
F = T + J + K
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]
\end{equation}
\end{beamerboxesrounded}
\begin{itemize}
\centering
\item $T$: Kinetic energy operator
\item $J$: Coulomb operator
\item $K$: Exchange operator
\item $f(i)$: Fock operator
\item $h(i)$: One electron Hamiltonian
\item $J_j(i)$: Coulomb operator
\item $K_j(i)$: Exchange operator
\end{itemize}
\pause[3]
\begin{beamerboxesrounded}[scheme=foncé]{}
\centering
Full Configuration Interaction gives access to high-order terms of the perturbation series!
Full Configuration Interaction gives access to high-order terms of the perturbation series !
\end{beamerboxesrounded}
\end{frame}
@ -160,9 +159,7 @@ Full Configuration Interaction gives access to high-order terms of the perturbat
\begin{figure}
\centering
\includegraphics[width=0.45\textwidth]{gill1986.png}
\caption{\centering Barriers to homolytic fission of \ce{He2^2+} at MPn/STO-3G level ($n = 1$--$20$).}
\label{fig:my_label}
\end{figure}
@ -186,7 +183,6 @@ Full Configuration Interaction gives access to high-order terms of the perturbat
\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.}
\label{tab:my_label}
\end{table}
\end{frame}
@ -355,12 +351,28 @@ The \textcolor{red}{radius of convergence} of the Taylor expansion of a function
\end{frame}
\begin{frame}{The Møller-Plesset Hamiltonian}
\begin{equation}
H(\lambda)=H_0 + \lambda (H_\text{phys} - H_0)
\end{equation}
\begin{equation}
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]
\end{equation}
\begin{equation}
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]
\end{equation}
\end{frame}
\begin{frame}{Existence of a critical point\footcite{stillinger_mollerplesset_2000}}
For $\lambda<0$:
\begin{equation*}
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]
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]
\end{equation*}
\end{frame}
@ -441,71 +453,7 @@ Proof of the existence of this group of sharp avoided crossings for Ne, He and H
\end{frame}
\section{The spherium model}
\begin{frame}{Spherium: a theoretical playground\footcite{loos_ground_2009}}
\begin{beamerboxesrounded}[scheme=foncé]{\centering Two electrons on a sphere Hamiltonian}
\begin{equation*}
H=-\frac{1}{2}(\grad_1^2 + \grad_2^2) + \frac{1}{r_{12}}
\end{equation*}
\end{beamerboxesrounded}
\vspace{0.5cm}
\begin{columns}
\column{0.48\textwidth}
\centering{Small $R$}
\vspace{0.5cm}
\begin{itemize}
\item $E_\text{kin} \gg E_\text{pot}$
\item Uniform density of electrons
\item \textcolor{red}{Weak correlation}
\end{itemize}
\vspace{0.5cm}
\column{0.48\textwidth}
\centering{Large $R$}
\vspace{0.5cm}
\begin{itemize}
\item $E_\text{kin} \ll E_\text{pot}$
\item Electrons on the opposite sides of the sphere
\item \textcolor{red}{Strong correlation}
\end{itemize}
\end{columns}
\end{frame}
\begin{frame}{Apparition of a class $\beta$ singularity}
\pause[1]
\begin{beamerboxesrounded}[scheme=foncé]{\centering Expectation}
The electrons are restricted to the surface of the sphere so we should not observe singularities characteristic of ionization processes.
\end{beamerboxesrounded}
\vspace{0.5cm}
\pause[2]
\large But for some values of R... we actually observe some $\beta$ singularities!
\centering Why?
\vspace{0.5cm}
\pause[3]
\begin{beamerboxesrounded}[scheme=foncé]{\centering Symmetry breaking}
The $\beta$ singularities observed are connected to the symmetry breaking of the wave function.
\end{beamerboxesrounded}
\end{frame}
\section{Conclusion}
\begin{frame}{Conclusion}
@ -515,20 +463,14 @@ The $\beta$ singularities observed are connected to the symmetry breaking of the
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.
\end{beamerboxesrounded}
\vspace{0.5cm}
\pause[2]
\vspace{0.5cm}
But there is an other secret application of exceptional points...
\pause[3]
\vspace{0.5cm}
\begin{beamerboxesrounded}[scheme=foncé]{\centering A new way to excited states energies}
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.
\begin{beamerboxesrounded}[scheme=foncé]{\centering Spherium: a theoretical playground}
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.
\end{beamerboxesrounded}
\end{frame}
\end{document}
\end{document}