Failures of TDDFT in describing the lowest intramolecular charge-transfer excitation in para-nitroaniline
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Failures of TDDFT in describing the lowest intramolecular charge-transfer excitation in para-nitroaniline. / Eriksen, Janus J.; Sauer, Stephan P. A.; Mikkelsen, Kurt Valentin; Christiansen, Ove; Jensen, Hans Jørgen Aagaard; Kongsted, Jacob.
I: Molecular Physics, Bind 111, Nr. 9-11, 2013, s. 1235-1248.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Failures of TDDFT in describing the lowest intramolecular charge-transfer excitation in para-nitroaniline
AU - Eriksen, Janus J.
AU - Sauer, Stephan P. A.
AU - Mikkelsen, Kurt Valentin
AU - Christiansen, Ove
AU - Jensen, Hans Jørgen Aagaard
AU - Kongsted, Jacob
PY - 2013
Y1 - 2013
N2 - We investigate the failure of Time{Dependent Density Functional Theory (TDDFT) with the CAM{B3LYP exchange{correlation (xc) functional coupled to the Polarizable Embedding (PE) scheme (PE-CAM-B3LYP) in reproducing the solvatochromic shift of the lowest intense charge{transfer excitation in para{nitroaniline (pNA) in water by comparing with results obtained with the Coupled Cluster Singles and Doubles (CCSD) model also coupled to the Polarizable Embedding scheme (PE-CCSD). We determine the amount of charge separation in the ground and excited charge{transfer state with both methods by calculating the electric dipole moments in the gas phase and for 100 solvent congurations. We find that CAM-B3LYP overestimates the amount of charge separation inherent in the ground state and TDDFT/CAM-B3LYP drastically underestimates this amount in the excited charge-transfer state. As the errors in the solvatochromatic shift are found to be inverse proportional to thechange in dipole moment upon excitation, we conclude that the flaws in the description of the solvatochromic shift of this excitation are related to TDDFT itself and how it responds to the solvent e¿ects modelled by the PE scheme. We recommend therefore to benchmark results of TDDFT calculations with CAM-B3LYP for intramolecular charge{transfer excitations in molecular systems similar to pNA against higher{level ab initio wave function methods, like, e.g., CCSD, prior to their use. Using the calculated change in dipole moment upon excitation as a measure for charge{transfer character, we furthermore conrm that the di¿erencebetween excitation energies calculated with TDDFT and with the Tamm-Danco¿ approximation (TDA) to TDDFT is indeed correlated with the charge-transfer character of a given electronic transition both in vacuo and in solution. This is supported by a corresponding correlation between the change in dipole moment and the size of the index diagnostic for the investigated CT excitation.
AB - We investigate the failure of Time{Dependent Density Functional Theory (TDDFT) with the CAM{B3LYP exchange{correlation (xc) functional coupled to the Polarizable Embedding (PE) scheme (PE-CAM-B3LYP) in reproducing the solvatochromic shift of the lowest intense charge{transfer excitation in para{nitroaniline (pNA) in water by comparing with results obtained with the Coupled Cluster Singles and Doubles (CCSD) model also coupled to the Polarizable Embedding scheme (PE-CCSD). We determine the amount of charge separation in the ground and excited charge{transfer state with both methods by calculating the electric dipole moments in the gas phase and for 100 solvent congurations. We find that CAM-B3LYP overestimates the amount of charge separation inherent in the ground state and TDDFT/CAM-B3LYP drastically underestimates this amount in the excited charge-transfer state. As the errors in the solvatochromatic shift are found to be inverse proportional to thechange in dipole moment upon excitation, we conclude that the flaws in the description of the solvatochromic shift of this excitation are related to TDDFT itself and how it responds to the solvent e¿ects modelled by the PE scheme. We recommend therefore to benchmark results of TDDFT calculations with CAM-B3LYP for intramolecular charge{transfer excitations in molecular systems similar to pNA against higher{level ab initio wave function methods, like, e.g., CCSD, prior to their use. Using the calculated change in dipole moment upon excitation as a measure for charge{transfer character, we furthermore conrm that the di¿erencebetween excitation energies calculated with TDDFT and with the Tamm-Danco¿ approximation (TDA) to TDDFT is indeed correlated with the charge-transfer character of a given electronic transition both in vacuo and in solution. This is supported by a corresponding correlation between the change in dipole moment and the size of the index diagnostic for the investigated CT excitation.
KW - Faculty of Science
KW - density functional theory
KW - electronic excitation
KW - SOLVATOCHROMISM
KW - Quantum Chemistry
KW - Computational Chemistry
KW - UV-VIS
U2 - 10.1080/00268976.2013.793841
DO - 10.1080/00268976.2013.793841
M3 - Journal article
VL - 111
SP - 1235
EP - 1248
JO - Molecular Physics
JF - Molecular Physics
SN - 0026-8976
IS - 9-11
ER -
ID: 45029321