diff --git a/Manuscript/FarDFT.tex b/Manuscript/FarDFT.tex index a6a337a..af19c0e 100644 --- a/Manuscript/FarDFT.tex +++ b/Manuscript/FarDFT.tex @@ -244,7 +244,7 @@ Equation \eqref{eq:dEdw} is our working equation for computing excitation energi \label{sec:func} The present work deals with the explicit construction of the (reduced) LDA xc functional $\e{\xc}{\bw}[\n{}{}]$ defined in Eq.~\eqref{eq:exc_def}. Here, we restrict our study to the case of a two-state ensemble (\ie, $\Nens = 2$) where both the ground state ($I=0$) and the first doubly-excited state ($I=1$) are considered. -The generalisation to a larger number of states is trivial and left for future work. +The generalisation to a larger number of states (in particular the inclusion of the first singly-excited state) is trivial and left for future work. We adopt the usual decomposition, and write down the weight-dependent xc functional as \begin{equation} @@ -259,11 +259,12 @@ Extension to spin-polarised systems will be reported in future work. \subsection{Weight-dependent exchange functional} \label{sec:Ex} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -We consider the ground- and doubly-excited states of the two-electron glomium system in its singlet ground state. +\titou{T2: More details required to understand what is glomium.} +We consider the ground- and doubly-excited states of the two-electron glomium system in its singlet ground state. \cite{Loos_2009a,Loos_2009c,Loos_2010e} These two states have the same (uniform) density $\n{}{} = 2/(2\pi^2 R^3)$ where $R$ is the radius of the glome onto which the electrons are confined. We refer the interested reader to Refs.~\onlinecite{Loos_2011b,Loos_2017a} for more details about this paradigm. -The reduced (\ie, per electron) Hartree-Fock (HF) energy for these two states is +The reduced (\ie, per electron) Hartree-Fock (HF) energies for these two states are \begin{subequations} \begin{align} \e{\HF}{(0)}(\n{}{}) & = \frac{4}{3} \qty(\frac{\n{}{}}{\pi})^{1/3}, @@ -292,11 +293,11 @@ with \end{align} \end{subequations} -Knowing that the exchange functional has the following form +In analogy with the conventional Dirac exchange functional, \cite{Dirac_1930} we write down the exchange functional of each individual state as \begin{equation} \e{\ex}{(I)}(\n{}{}) = \Cx{(I)} \n{}{1/3}, \end{equation} -we obtain +and we then obtain \begin{align} \Cx{(0)} & = - \frac{4}{3} \qty( \frac{1}{\pi} )^{1/3}, & @@ -316,7 +317,7 @@ with \begin{equation} \Cx{\ew{}} = (1-\ew{}) \Cx{(0)} + \ew{} \Cx{(1)}. \end{equation} -Quite remarkably, the weight dependence of the exchange functional can be transferred to the $\Cx{}$ coefficient, which is expected from a theoretical point of view but also a nice property from a more practical aspect. +Quite remarkably, the weight dependence of the exchange functional can be transferred to the $\Cx{}$ coefficient, which is expected from a theoretical point of view, yet a nice property from a more practical aspect. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% @@ -329,7 +330,7 @@ Based on highly-accurate calculations, \cite{Loos_2009a,Loos_2009c,Loos_2010e} o \label{eq:ec} \e{\co}{(I)}(\n{}{}) = \frac{a_1^{(I)}}{1 + a_2^{(I)} \n{}{-1/6} + a_3^{(I)} \n{}{-1/3}}, \end{equation} -where the $a_k^{(I)}$'s are state-specific fitting parameters, which are provided in Table \ref{tab:OG_func}. +where $a_2^{(I)}$ and $a_3^{(I)}$ are state-specific fitting parameters, which are provided in Table \ref{tab:OG_func}. The value of $a_1^{(I)}$ is obtained via the exact high-density expansion of the correlation energy. \cite{Loos_2011b} Equation \eqref{eq:ec} is depicted in Fig.~\ref{fig:Ec} for each state alongside the data gathered in Table \ref{tab:Ref}. @@ -343,7 +344,7 @@ Combining these, we build a two-state weight-dependent correlation functional: \begin{figure} \includegraphics[width=\linewidth]{fig1} \caption{ - Reduced (i.e., per electron) correlation energy $\e{\co}{(I)}$ [see Eq.~\eqref{eq:ec}] as a function of $R = 1/(\pi \n{}{})^{1/3}$ for the ground state ($I=0$), and the first doubly-excited state ($I=1$) of the (spin-unpolarized) two-electron glomium system. + Reduced (i.e., per electron) correlation energy $\e{\co}{(I)}$ [see Eq.~\eqref{eq:ec}] as a function of $R = 1/(\pi \n{}{})^{1/3}$ for the ground state ($I=0$), and the first doubly-excited state ($I=1$) of the (spin-unpolarized) two-electron FUEG. The data gathered in Table \ref{tab:Ref} are also reported. } \label{fig:Ec} @@ -354,7 +355,7 @@ Combining these, we build a two-state weight-dependent correlation functional: \begin{table} \caption{ \label{tab:Ref} - $-\e{\co}{(I)}$ as a function of the radius of the glome $R = 1/(\pi \n{}{})^{1/3}$ for the ground state ($I=0$), and the first doubly-excited state ($I=1$) of the (spin-unpolarized) two-electron glomium system. + $-\e{\co}{(I)}$ as a function of the radius of the glome $R = 1/(\pi \n{}{})^{1/3}$ for the ground state ($I=0$), and the first doubly-excited state ($I=1$) of the (spin-unpolarized) two-electron FUEG. } \begin{ruledtabular} \begin{tabular}{lcc} @@ -381,7 +382,8 @@ Combining these, we build a two-state weight-dependent correlation functional: \begin{table} \caption{ \label{tab:OG_func} - Parameters of the correlation DFAs defined in Eq.~\eqref{eq:ec}.} + Parameters of the correlation functionals for each individual state defined in Eq.~\eqref{eq:ec}. + The values of $a_1$ are obtained to reproduce the exact high density correlation energy of each individual state, while $a_2$ and $a_3$ are fitted on the numerical values reported in Table \ref{tab:Ref}.} \begin{ruledtabular} \begin{tabular}{lcc} & \tabc{Ground state} & \tabc{Doubly-excited state} \\