Assessing the accuracy of simplified coupled cluster methods for electronic excited states in f0 actinide compounds

We scrutinize the performance of different variants of equation of motion coupled cluster (EOM-CC) methods to predict electronic excitation energies and excited state potential energy surfaces in closed-shell actinide species. We focus our analysis on various recently presented pair coupled cluster...

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Bibliographic Details
Published inPhysical chemistry chemical physics : PCCP Vol. 21; no. 35; pp. 1939 - 1953
Main Authors Nowak, Artur, Tecmer, Pawe, Boguslawski, Katharina
Format Journal Article
LanguageEnglish
Published England Royal Society of Chemistry 21.09.2019
Subjects
Accuracy
Adiabatic flow
Chemical bonds
Clusters
Coupling (molecular)
Electronic spectra
Equations of motion
Error analysis
Excitation
Flavors
Potential energy
Protactinium
Thorium
Thorium oxides
Uranium
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Summary:We scrutinize the performance of different variants of equation of motion coupled cluster (EOM-CC) methods to predict electronic excitation energies and excited state potential energy surfaces in closed-shell actinide species. We focus our analysis on various recently presented pair coupled cluster doubles (pCCD) models [ J. Chem. Phys. , 2016, 23 , 234105 and J. Chem. Theory Comput. , 2019, 15 , 18-24] and compare their performance to the conventional EOM-CCSD approach and to the completely renormalized EOM-CCSD with perturbative triples ansatz. Since the single-reference pCCD model allows us to efficiently describe static/nondynamic electron correlation, while dynamical electron correlation is accounted for a posteriori , the investigated pCCD-based methods represent a good compromise between accuracy and computational cost. Such a feature is particularly advantageous when modelling electronic structures of actinide-containing compounds with stretched bonds. Our work demonstrates that EOM-pCCD-based methods reliably predict electronic spectra of small actinide building blocks containing thorium, uranium, and protactinium atoms. Specifically, the standard errors in adiabatic and vertical excitation energies obtained by the conventional EOM-CCSD approach are reduced by a factor of 2 when employing the EOM-pCCD-LCCSD variant resulting in a mean error of 0.05 eV and a standard deviation of 0.25 eV. We scrutinize the performance of different variants of equation of motion coupled cluster (EOM-CC) methods to predict electronic excitation energies and excited state potential energy surfaces in closed-shell actinide species.
Bibliography:C
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2v
NUN, and ThO
and ThO
Electronic supplementary information (ESI) available: Excited state potential energy surfaces, total electronic energies, and excitation energies for all investigated molecules. Error measures for total electronic energies and excitation energies along the potential energy surface as well as for adiabatic excitation energies for each investigated compound. Vertical excitation energies for UO
point group symmetry for UO
2
2h
and
10.1039/c9cp03678d
using a TZ-quality basis set. pCCD, EOM-pCCD+S, EOM-pCCD-CCS, and EOM-pCCD-LCCSD calculations imposing
2+
respectively, timings for various flavours of excited state models, and a summary of existing experimental spectroscopic parameters of the investigated molecules. See DOI
ObjectType-Article-1
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ISSN:1463-9076
1463-9084
DOI:10.1039/c9cp03678d