diff --git a/Manuscript/eDFT.tex b/Manuscript/eDFT.tex index 91ee865..524228d 100644 --- a/Manuscript/eDFT.tex +++ b/Manuscript/eDFT.tex @@ -4,6 +4,7 @@ \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{txfonts} +\usepackage{mathrsfs} \usepackage[ colorlinks=true, @@ -769,7 +770,7 @@ What do you think?} Combining Eq.~\eqref{eq:exact_ind_ener_rdm} with Eq.~\eqref{eq:eLDA_corr_fun} leads to our final energy level expression within KS-eLDA: \beq\label{eq:EI-eLDA} \begin{split} - \E{\titou{eLDA}}{(I)} + \E{{eLDA}}{(I)} & = \E{HF}{(I)} \\ @@ -781,17 +782,31 @@ Combining Eq.~\eqref{eq:exact_ind_ener_rdm} with Eq.~\eqref{eq:eLDA_corr_fun} le \left. \pdv{\e{c}{{\bw}}(\n{}{})}{\n{}{}} \right|_{\n{}{} = \n{\bGam{\bw}}{}(\br{})} d\br{} \\ & + \int \sum_{K>0} \qty(\delta_{IK} - \ew{K} ) \n{\bGam{\bw}}{}(\br{}) - \left. \pdv{\e{c}{\bw}(\n{}{})}{\ew{K}} \right|_{\n{}{}=\n{\bGam{\bw}}{}(\br{})} d\br{}. + \left. \pdv{\e{c}{\bw}(\n{}{})}{\ew{K}} \right|_{\n{}{}=\n{\bGam{\bw}}{}(\br{})} d\br{}, \end{split} \eeq -\titou{T2: I think we should specify what those terms are physically... Maybe earlier in the manuscript?} where \beq \E{HF}{(I)}=\Tr[\bGam{(I)} \bh] + \frac{1}{2} \Tr[\bGam{(I)} \bG \bGam{(I)}] \eeq -is the analog for ground {\it and} excited states of the HF energy. -Let us stress that, to the best of our knowledge, eLDA is the first -density-functional approximation that incorporates weight +is the analog for ground and excited states (within an ensemble) of the HF energy. +If, for analysis purposes, we Taylor expand the density-functional +correlation contributions +around the $I$th KS state density +$\n{\bGam{(I)}}{}(\br{})$, the sum of +the second and third terms on the right-hand side +of Eq.~\eqref{eq:EI-eLDA} can be simplified as follows through first order in +$\n{\bGam{\bw}}{}(\br{})-\n{\bGam{(I)}}{}(\br{})$: +\beq +\int \e{c}{\bw}(\n{\bGam{(I)}}{}(\br{})) \n{\bGam{(I)}}{}(\br{}) d\br{} ++\mathcal{O}\left([\n{\bGam{\bw}}{}-\n{\bGam{(I)}}{}]^2\right), +\eeq +and it can therefore be identified as +an individual-density-functional correlation energy where the density-functional +correlation energy per particle is approximated by the ensemble one for +all the states within the ensemble. +Let us finally stress that, to the best of our knowledge, eLDA is the first +density-functional approximation that incorporates ensemble weight dependencies explicitly, thus allowing for the description of derivative discontinuities [see Eq.~\eqref{eq:excited_ener_level_gs_lim} and the comment that follows] {\it via} the last term on the right-hand side