revision and response letter

Manuscript/QUEST_WIREs.tex

@@ -131,7 +131,7 @@ systems \cite{vanSetten_2013,Bruneval_2016,Caruso_2016,Govoni_2018}. The extrapo
 of atoms and small molecules (without experimental data) is yet another successful example of benchmark set \cite{Tajti_2004,Bomble_2006,Harding_2008}. More recently, let us mention the benchmark datasets
 of the \textit{Simons Collaboration on the Many-Electron Problem} providing, for example, highly-accurate ground-state energies for
 hydrogen chains \cite{Motta_2017} as well as transition metal atoms and their ions and monoxides \cite{Williams_2020}. 
-Let us also mention the set of Zhao and Truhlar for small transition metal complexes employed to compare the accuracy of density-functional methods \cite{ParrBook} for $3d$ transition-metal chemistry \cite{Zhao_2006}, \alert{the MGCDB84 molecular database of Mardirossian and Head-Gordon that they use to benchmark a total of 200 density functionals and design (using combinatorial approach) the $\omega$B97M-V functional \cite{Mardirossian_2017},} and finally the popular GMTKN24 \cite{Goerigk_2010},
+Let us also mention the set of Zhao and Truhlar for small transition metal complexes employed to compare the accuracy of density-functional methods \cite{ParrBook} for $3d$ transition-metal chemistry \cite{Zhao_2006}, \alert{the MGCDB84 molecular database of Mardirossian and Head-Gordon that they use to benchmark a total of 200 density functionals and design (using a combinatorial approach) the $\omega$B97M-V functional \cite{Mardirossian_2017},} and finally the popular GMTKN24 \cite{Goerigk_2010},
 GMTKN30 \cite{Goerigk_2011a,Goerigk_2011b} and GMTKN55 \cite{Goerigk_2017} databases for general main group thermochemistry, kinetics, and non-covalent interactions developed by Goerigk, Grimme and
 their coworkers.
 
@@ -248,7 +248,7 @@ Below, we provide a much cleaner way of estimating the extrapolation error in SC
 The particularity of the current implementation is that the selection step and the PT2 correction are computed \textit{simultaneously} via a hybrid semistochastic algorithm \cite{Garniron_2017,Garniron_2019}.
 Moreover, a renormalized version of the PT2 correction (dubbed rPT2) has been recently implemented for a more efficient extrapolation to the FCI limit \cite{Garniron_2019}.
 We refer the interested reader to Ref.~\cite{Garniron_2019} where one can find all the details regarding the implementation of the CIPSI algorithm.
-Note that all our SCI wave functions are eigenfunctions of the $\Hat{S}^2$ spin operator which is, unlike ground-state calculations, paramount in the case of excited states \cite{Applencourt_2018}.
+\alert{Note that all our SCI wave functions are eigenfunctions of the $\Hat{S}^2$ spin operator which is, unlike ground-state calculations, paramount in the case of excited states \cite{Applencourt_2018}. In the case of ground-state calculations, this constraint can be relaxed without altering the final result (see, for example, Ref.~\cite{Loos_2020e}).}
 
 %------------------------------------------------
 \subsubsection{Benchmarked computational methods}
@@ -1183,6 +1183,8 @@ Additionally, we also provide a specific analysis for each type of excited state
 Hence, the statistical values are reported for various types of excited states and molecular sizes for the MSE and MAE.
 The distribution of the errors in vertical excitation energies (with respect to the TBE/aug-cc-pVTZ reference values) are represented in Fig.~\ref{fig:QUEST_stat} for all the ``safe'' excitations having a dominant single excitation character (\ie, the double excitations are discarded).
 Similar graphs are reported in the {\SupInf} for specific sets of transitions and molecules.
+\alert{The comparison between methods presented here is performed for Franck-Condon geometries only.
+Then, it is important to stress that the present method ranking might change significantly when moving away from the Franck-Condon region as most excited-state methods do not provide a uniform description of potential energy surfaces.}
 
 %%% TABLE IV %%%
 \begin{sidewaystable}
@@ -1314,10 +1316,14 @@ Paraphrasing Thiel's conclusions \cite{Schreiber_2008}, we hope that not only th
 In this framework, we provide in the {\SupInf} a file with all our benchmark data.
 
 Regarding future improvements and extensions, we would like to mention that although our present goal is to produce chemically accurate vertical excitation energies, we are currently devoting great efforts to obtain highly-accurate excited-state properties \cite{Hodecker_2019,Eriksen_2020b} such as dipoles and oscillator strengths for molecules of small and medium sizes \cite{Chrayteh_2021,Sarkar_2021}, so as to complete previous efforts aiming at determining accurate excited-state geometries \cite{Budzak_2017,Jacquemin_2018}.
+\alert{In this context, methods for which one has access to analytic nuclear gradients [\eg, ADC(2) and CC2] and frequencies [\eg, EOM-CCSD] have an indisputable edge.}
 Reference ground-state properties (such as correlation energies and atomization energies) are also being currently produced \cite{Scemama_2020,Loos_2020e}.
+\alert{Additional reference energies for charge-transfer excited states \cite{Kozma_2020} and transition metal compounds \cite{Zhao_2006,Williams_2020} would be a valuable addition to the present database.}
 Besides this, because computing 500 (or so) excitation energies can be a costly exercise even with cheap computational methods, we are planning on developing a ``diet set'' (\ie, a much smaller set of excitation energies which can reproduce key results of the full QUEST database, including ranking of approximations) following the philosophy of the ``diet GMTKN55'' set proposed recently by Gould \cite{Gould_2018b}.
 We hope to report on this in the near future.
 
+
+
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 %\section*{acknowledgements}
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Response_Letter/Response_Letter.tex

@@ -47,20 +47,20 @@ We look forward to hearing from you.
 	It is then essential to stress that the ranking of the electronic structure methods (as nicely illustrated in Fig. 5) might change significantly when moving away from the Franck-Condon region. 
 	Most electronic structure methods for excited states cannot provide a uniform description of potential energy surfaces, being more accurate in certain regions than in others.}
 	\\
-	\alert{We have added a comment.}
+	\alert{We have added a comment in the benchmarks section.}
 	
 	\item 
 	{The discussion is based on electronic energies. 
 	While electronic energies are important, investigation of excited electronic state often requires additional quantities due to the importance played by nuclear motion and coordinates. 
 	Some of this is already discussed in substance in the last paragraph of the conclusion, but offering some information about which methods can provide nuclear gradients or Hessians would be valuable for the reader.}
 	\\
-	\alert{A coupled of sentences have been added to clarity this point.}
+	\alert{A sentence has been added to clarity this point in the concluding section.}
  
 	\item 
 	{While many different molecules are discussed in this work, I think that a caveat about the performance of some of the methods presented for other families of molecules might be welcome. 
 	(The authors mention a few different types of molecules in the introduction, but it might be interesting to stress them at the end of this work too.)}
 	\\
-	\alert{}
+	\alert{Another comment has been added in the concluding section.}
 	
 \end{itemize}
 
@@ -90,7 +90,7 @@ We look forward to hearing from you.
 	\item 
 	{MGCDB84 by Madirossian and Head-Gordon [10.1080/00268976.2017.1333644] seems to be missing (or at least not highlighted) from the list of ground state benchmark sets despite being one of the largest.}
 	\\
-	\alert{The reviewer is right. The work of Madirossian and Head-Gordon has been mentioned in the Introduction.}
+	\alert{The reviewer is right. The work of Madirossian and Head-Gordon is now mentioned and cited in the Introduction.}
 	
 	\item 
 	{p6: The third paragraph is a lot to take in and should probably be split into two or three paragraphs to make reading a bit easier.}
@@ -101,7 +101,7 @@ We look forward to hearing from you.
 	{p7 line 47-48: The wording of the final sentence on this page makes spin-symmetry breaking sound acceptable. 
 	While I don't disagree that some (perhaps most) quantum chemists would agree, for those of us on the opposing side I'd like to see a caveat (e.g. which is, unlike common wisdom about).}
 	\\
-	\alert{}
+	\alert{This comment has been reworded accordingly.}
 
 	\item 
 	{p10-11: Final/start paragraph of p10/p11 should probably be split into two or three.}
@@ -116,14 +116,15 @@ We look forward to hearing from you.
 	\item 
 	{Table 2: I would suggest to use italic numbers for "unsafe" TBE so that readers can easily identify them.}
 	\\
-	\alert{Done.}
+	\alert{There is already a label Y/N to identify the unsafe TBEs, so we would prefer to leave it as it is.
+	Moreover, these data can be also extracted from the website (there is a box to select only the safe TBEs) or the excel spreadsheet provided as supplementary material.}
 		
 	\item 
 	{Table 4: This is purely a matter of taste and 100\% optional given that the authors provide online access to data. 
 	But, I think readers might benefit from having the table reported as two horizontal panels, with one reporting up to CC3 and the other the rest. 
 	The reason being that many people now read on a screen, where rotation is more annoying than on paper.}
 	\\
-	\alert{These data are also reported as supplementary materials, so we propose to leave Table 4 as it is.}
+	\alert{Again, these data are also reported as supplementary material, so we propose to leave Table 4 as it is.}
 		
 	\item 
 	{Figure 5: This is an excellent figure!}