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Pierre-Francois Loos 2020-02-17 23:24:51 +01:00
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commit 37437c2f4d
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@ -244,7 +244,11 @@ where the KS wavefunctions fulfill the ensemble density constraint
\eeq
The (approximate) description of the correlation part is discussed in Sec.~\ref{sec:eDFA}.
In practice, the ensemble energy is not the most interesting quantity, and one is more concerned with excitation energies or individual energy levels (for geometry optimizations, for example).
In practice, the ensemble energy is not the most interesting quantity, and one is more concerned with excitation energies
\beq
\Ex{(I)} = \E{}{(I)} - \E{}{(0)},
\eeq
or individual energy levels (for geometry optimizations, for example).
The latter can be extracted exactly as follows~\cite{}
\beq\label{eq:indiv_ener_from_ens}
\E{}{(I)} = \E{}{\bw} + \sum_{K>0} \qty(\delta_{IK} - \ew{K} ) \pdv{\E{}{\bw}}{\ew{K}},
@ -908,7 +912,7 @@ Even for larger boxes, the discrepancy between FCI and eLDA for double excitatio
\end{figure}
%%% %%% %%%
\titou{Need further discussion on DD and LZ shift. Linearity of energy wrt weights?}
\titou{Need further discussion on DD.}
\titou{For small $L$, the single and double excitations are ``pure''. In other words, the excitation is dominated by a single reference Slater determinant.
However, when the box gets larger, there is a strong mixing between different degree of excitations.

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