little work

Manuscript/ExPerspective.bib

@@ -1,7 +1,7 @@
 %% This BibTeX bibliography file was created using BibDesk.
 %% http://bibdesk.sourceforge.net/
 
-%% Created for Pierre-Francois Loos at 2019-10-31 16:08:35 +0100 
+%% Created for Pierre-Francois Loos at 2019-11-01 17:00:17 +0100 
 
 
 %% Saved with string encoding Unicode (UTF-8) 
@@ -82,6 +82,51 @@
 @string{theo = {J. Mol. Struct. (THEOCHEM)}}
 
 
+@article{Kan17,
+	Author = {K{\'a}nn{\'a}r, D{\'a}niel and Tajti, Attila and Szalay, P{\'e}ter G.},
+	Date-Added = {2019-11-01 17:00:12 +0100},
+	Date-Modified = {2019-11-01 17:00:12 +0100},
+	Doi = {10.1021/acs.jctc.6b00875},
+	Eprint = {http://dx.doi.org/10.1021/acs.jctc.6b00875},
+	Journal = {J. Chem. Theory Comput.},
+	Number = {1},
+	Pages = {202--209},
+	Title = {Accuracy of Coupled Cluster Excitation Energies in Diffuse Basis Sets},
+	Url = {http://dx.doi.org/10.1021/acs.jctc.6b00875},
+	Volume = {13},
+	Year = {2017},
+	Bdsk-Url-1 = {http://dx.doi.org/10.1021/acs.jctc.6b00875}}
+
+@article{Kan14,
+	Author = {K{\'a}nn{\'a}r, D{\'a}niel and Szalay, P{\'e}ter G.},
+	Date-Added = {2019-11-01 17:00:12 +0100},
+	Date-Modified = {2019-11-01 17:00:12 +0100},
+	Doi = {10.1021/ct500495n},
+	Eprint = {http://dx.doi.org/10.1021/ct500495n},
+	Journal = {J. Chem. Theory Comput.},
+	Number = {9},
+	Pages = {3757-3765},
+	Title = {Benchmarking Coupled Cluster Methods on Valence Singlet Excited States},
+	Url = {http://dx.doi.org/10.1021/ct500495n},
+	Volume = {10},
+	Year = {2014},
+	Bdsk-Url-1 = {http://dx.doi.org/10.1021/ct500495n}}
+
+@article{Wat13,
+	Author = {Watson, Thomas J. and Lotrich, Victor F. and Szalay, Peter G. and Perera, Ajith and Bartlett, Rodney J.},
+	Date-Added = {2019-11-01 16:50:05 +0100},
+	Date-Modified = {2019-11-01 16:50:05 +0100},
+	Doi = {10.1021/jp308634q},
+	Eprint = {http://dx.doi.org/10.1021/jp308634q},
+	Journal = {J. Phys. Chem. A},
+	Number = {12},
+	Pages = {2569-2579},
+	Title = {Benchmarking for Perturbative Triple-Excitations in EE-EOM-CC Methods},
+	Url = {http://dx.doi.org/10.1021/jp308634q},
+	Volume = {117},
+	Year = {2013},
+	Bdsk-Url-1 = {http://dx.doi.org/10.1021/jp308634q}}
+
 @article{Tro99,
 	Author = {A. B. Trofimov and G. Stelter and J. Schirmer},
 	Date-Added = {2019-10-31 15:04:29 +0100},

Manuscript/ExPerspective.tex

@@ -208,17 +208,17 @@ This has drastic consequences such as, for example, the complete absence of doub
 %%% SCI METHODS %%%
 %%%%%%%%%%%%%%%%%%%
 
-Alternatively to CC and multiconfigurational methods, one can also compute transition energies for various types of excited states using selected configuration interaction (sCI) methods \cite{Ben69,Whi69,Hur73} which have recently demonstrated their ability to reach near full CI (FCI) quality energies for small molecules \cite{Gin13,Gin15,Caf16,Gar17b,Hol16,Sha17,Hol17,Chi18,Sce18,Sce18b,Loo18a,Gar18}.
+Alternatively to CC and multiconfigurational methods, one can also compute transition energies for various types of excited states using selected configuration interaction (SCI) methods \cite{Ben69,Whi69,Hur73} which have recently demonstrated their ability to reach near full CI (FCI) quality energies for small molecules \cite{Gin13,Gin15,Caf16,Gar17b,Hol16,Sha17,Hol17,Chi18,Sce18,Sce18b,Loo18a,Gar18}.
 The idea behind such methods is to avoid the exponential increase of the size of the CI expansion by retaining the most energetically relevant determinants only, thanks to the use of a second-order energetic criterion to select perturbatively determinants in the FCI space.
 However, although the \textit{``exponential wall''} is pushed back, this type of methods is only applicable to molecules with a small number of heavy atoms with relatively compact basis sets.
 
 
-In the past five years, we have witnessed a resurgence of selected CI (sCI) methods thanks to the development and implementation of new and fast algorithm to select cleverly determinants in the FCI space.
-sCI methods rely on the same principle as the usual CI approach, except that determinants are not chosen a priori based on occupation or excitation criteria but selected among the entire set of determinants based on their estimated contribution to the FCI wave function. 
+In the past five years, we have witnessed a resurgence of selected CI (SCI) methods thanks to the development and implementation of new and fast algorithm to select cleverly determinants in the FCI space.
+SCI methods rely on the same principle as the usual CI approach, except that determinants are not chosen a priori based on occupation or excitation criteria but selected among the entire set of determinants based on their estimated contribution to the FCI wave function. 
 Indeed, it has been noticed long ago that, even inside a predefined subspace of determinants, only a small number of them significantly contributes.
-Therefore, an on-the-fly selection of determinants is a rather natural idea that has been proposed in the late 1960's by Bender and Davidson as well as Whitten and Hackmeyer's sCI methods are still very much under active development. 
-The main advantage of sCI methods is that no a priori assumption is made on the type of electronic correlation. 
-Therefore, at the price of a brute force calculation, a sCI calculation is less biased by the user's appreciation of the problem's complexity.
+Therefore, an on-the-fly selection of determinants is a rather natural idea that has been proposed in the late 1960's by Bender and Davidson as well as Whitten and Hackmeyer's SCI methods are still very much under active development. 
+The main advantage of SCI methods is that no a priori assumption is made on the type of electronic correlation. 
+Therefore, at the price of a brute force calculation, a SCI calculation is less biased by the user's appreciation of the problem's complexity.
 The approach that we have implemented in QUANTUM PACKAGE is based on the CIPSI algorithm developed by Huron, Rancurel, and Malrieu in 1973.
 
 %%%%%%%%%%%%%%%
@@ -237,25 +237,35 @@ Although people usually don't really like reading, reviewing or even the idea of
 %%%%%%%%%%%%%%%%%%%
 A major contribution originates from the Thiel's group \cite{Sch08,Sil08,Sau09,Sil10b,Sil10c} with the introduction of the so-called Thiel's set of excitation energies. \cite{Sch08}
 For the first time, this benchmark set gathers a large number of excitation energies consisting of 28 medium-size organic molecules with a total of 223 excited states (152 singlet and 71 triplet states).
-In their first study they performed CC2, EOM-CCSD, CC3 and MS-CASPT2 calculations in order to provide (based on additional high-level literature data) best theoretical estimates (TBE).
+In their first study they performed CC2, EOM-CCSD, CC3 and MS-CASPT2 calculations (in the TZVP basis) in order to provide (based on additional high-level literature data) best theoretical estimates (TBEs).
+Their main conclusion was that \textit{``CC3 and CASPT2 excitation energies are in excellent agreement for states which are dominated by single excitations''}.
 These TBEs were later refined with the larger aug-cc-pVTZ basis set. \cite{Sil10b}
+As evidenced of the values of reference data, these TBEs were quickly applied to benchmark various computationally effective methods (see Ref.~\onlinecite{Loo18a} and references therein).
+
+Theoretical improvements were slow but steady.
+In 2013, Watson et al.\cite{Wat13} proposed for EOM-CCSDT-3/TZVP (which corresponds to an iterative approximation of the triples from EOM-CCSDT) excitation energies for the Thiel's set.
+Their quality were very similar to the CC3 values reported in Ref.~\onlinecite{Sau09} and the authors could not appreciate which ones were the most accurate.
+Similarly, Dreuw and coworkers performed ADC(3) calculations on Thiel?s set and arrived at the same kind of conclusion: \cite{Har14}
+\textit{``based on the quality of the existing benchmark set it is practically not possible to judge whether ADC(3) or CC3 is more accurate''}
+Finally, let us mention the work of Kannar and Szalay who reported EOM-CCSDT (with TZVP \cite{Kan14} and aug-cc-pVTZ \cite{Kan17}) for a subset of the original Thiel's set. 
+Our recent contribution \cite{Loo18a} has been able to bring answers to this question.
 
 %%%%%%%%%%%%%%%%%%%%%%%
 %%% JACQUEMIN'S SET %%%
 %%%%%%%%%%%%%%%%%%%%%%%
-Very recently, we also made a contribution to this quest for highly-accurate excitation energies. \cite{Loo18a}
+Indeed, very recently, we also made a contribution to this quest for highly-accurate excitation energies. \cite{Loo18a}
 We studied 18 small molecules (water, hydrogen sulfide, ammonia, hydrogen chloride, dinitrogen, carbon monoxide, acetylene, ethylene, formaldehyde, methanimine, thioformaldehyde, acetaldehyde, cyclopropene, diazomethane, formamide, ketene, nitrosomethane, and the smallest streptocyanine) with sizes ranging from one to three nonhydrogen atoms. 
-For such systems, using sCI expansions of several million determinants, we were able to compute more than 100 highly accurate vertical excitation energies with typically augmented triple-$\zeta$ basis sets. 
+For such systems, using SCI expansions of several million determinants, we were able to compute more than 100 highly accurate vertical excitation energies with typically augmented triple-$\zeta$ basis sets. 
 It allowed us to benchmark a series of 12 state-of-the-art excited-state wave function methods accounting for double and triple excitations.
 We use this series theoretical best estimates to benchmark a series of popular methods for excited state calculations [CIS(D), ADC(2), CC2, STEOM-CCSD, CCSD, CCSDR(3), and CCSDT-3]. 
 
 Even more recently, we provided accurate reference excitation energies for transitions involving a substantial amount of double excitation using a series of increasingly large diffuse-containing atomic basis sets. \cite{Loo19c}
 Our set gathered 20 vertical transitions from 14 small- and medium-sized molecules (acrolein, benzene, beryllium atom, butadiene, carbon dimer and trimer, ethylene, formaldehyde, glyoxal, hexatriene, nitrosomethane, nitroxyl, pyrazine, and tetrazine). 
 For the smallest molecules, we were able to obtain well converged excitation energies with an augmented quadruple-$\zeta$ basis set, while only augmented double-$\zeta$ bases were manageable for the largest systems (such as acrolein, butadiene, hexatriene, and benzene). 
-Note that the largest sCI expansion considered in this study had more than 200 million determinants.
+Note that the largest SCI expansion considered in this study had more than 200 million determinants.
 
 In order to push further our analysis to larger compounds, we provided highly-accurate vertical transition energies obtained for 27 molecules encompassing 4, 5, and 6 non-hydrogen atoms (acetone, acrolein, benzene, butadiene, cyanoacetylene, cyanoformaldehyde, cyanogen, cyclopentadiene, cyclopropenone, cyclopropenethione, diacetylene, furan, glyoxal, imidazole, isobutene, methylenecyclopropene, propynal, pyrazine, pyridazine, pyridine, pyrimidine, pyrrole, tetrazine, thioacetone, thiophene, thiopropynal, and triazine). 
-To obtain these energies, we use CC approaches up to the highest possible order (CC3, CCSDT, and CCSDTQ), sCI approach up to several millions determinants, and NEVPT2. 
+To obtain these energies, we use CC approaches up to the highest possible order (CC3, CCSDT, and CCSDTQ), SCI approach up to several millions determinants, and NEVPT2. 
 All approaches being combined with diffuse-containing atomic basis sets. 
 For all transitions, we report at least CC3/aug-cc-pVQZ transition energies and as well as CC3/aug-cc-pVTZ oscillator strengths for all dipole-allowed transitions. 
 We show that CC3 almost systematically delivers transition energies in agreement with higher-level of theories ($\pm 0.04$ eV) but for transitions presenting a dominant double excitation character.