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Improving convergence of experimental and computed vertical ionization energies using the ionization potential equation‐of‐motion coupled‐cluster with singles and doubles method
Author(s) -
Buzzanca Marissa,
Brummeyer Brandon,
Gutow Jonathan H.
Publication year - 2020
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.26261
Subject(s) - ionization , adiabatic process , computation , coupled cluster , limit (mathematics) , position (finance) , atomic physics , basis set , ionization energy , basis (linear algebra) , work (physics) , physics , computational physics , chemistry , ion , quantum mechanics , molecule , mathematics , geometry , mathematical analysis , algorithm , finance , economics
Comparison of statistically evaluated experimental vertical ionization energies (IEs) for 53 medium‐sized molecules (6‐34 atoms) with ionization potential equation‐of‐motion coupled‐cluster with singles and doubles (IP‐EOMCCSD) computations shows that discrepancies between computed and experimental results can be accounted for with a combination of experimental and theoretical contributions. Discrepancies can be minimized by extrapolating computations to the complete basis set limit and correcting for vibrational zero‐point energy (ZPE) while comparing with experimental IEs calculated as the intensity‐weighted mean band position to account for band asymmetries. This procedure reduced the average discrepancy for ethylene, ( E )‐2‐butene, 2,5‐dihydrofuran, and pyrrole from 0.25 to 0.05 eV. Agreement between reported vertical IEs and computations without either making adjustments as described in this paper or using complete simulation of the ionization spectrum should be considered fortuitous. The comparisons made in this work show that estimates of vertical and adiabatic IE made using IP‐EOMCCSD extrapolated to the complete basis set limit and corrected for vibrational ZPE can be used with reasonable confidence when experimental values are not available.