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Rights statement: This is an Accepted Manuscript of an article published by Taylor & Francis in Molecular Physics on 08/04/2018, available online: http://www.tandfonline.com/10.1080/00268976.2018.1453094
Accepted author manuscript, 246 KB, PDF document
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Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Molecular excited states from the SCAN functional
AU - Tozer, David J.
AU - Peach, Michael Joseph George
N1 - This is an Accepted Manuscript of an article published by Taylor & Francis in Molecular Physics on 08/04/2018, available online: http://www.tandfonline.com/10.1080/00268976.2018.1453094
PY - 2018/4
Y1 - 2018/4
N2 - The performance of the strongly constrained and appropriately normed (SCAN) [Phys. Rev. Lett.115, 036402 (2015)] meta-generalised gradient approximation exchange–correlation functional isinvestigated for the calculation of time-dependent density-functional theory (TDDFT) molecularexcitation energies of local, charge-transfer, and Rydberg character, together with the excited 3Σ+u potential energy curve in H2. The SCAN results frequently resemble those obtained using a global hybrid functional, with either a standard or increased fraction of exact orbital exchange. Forlocal excitations, SCAN can exhibit significant triplet instability problems, resulting in imaginarytriplet excitation energies for a number of cases. The Tamm–Dancoff approximation offers a simple approach to improve the situation, but the excitation energies are still significantly underestimated.Understanding the origin of these (near)-triplet instabilities may provide useful insight into futurefunctional development.
AB - The performance of the strongly constrained and appropriately normed (SCAN) [Phys. Rev. Lett.115, 036402 (2015)] meta-generalised gradient approximation exchange–correlation functional isinvestigated for the calculation of time-dependent density-functional theory (TDDFT) molecularexcitation energies of local, charge-transfer, and Rydberg character, together with the excited 3Σ+u potential energy curve in H2. The SCAN results frequently resemble those obtained using a global hybrid functional, with either a standard or increased fraction of exact orbital exchange. Forlocal excitations, SCAN can exhibit significant triplet instability problems, resulting in imaginarytriplet excitation energies for a number of cases. The Tamm–Dancoff approximation offers a simple approach to improve the situation, but the excitation energies are still significantly underestimated.Understanding the origin of these (near)-triplet instabilities may provide useful insight into futurefunctional development.
KW - Density-functional theory
KW - exchange–correlation functionals
KW - time-dependent DFT
KW - excited states
KW - triplet instabilities
U2 - 10.1080/00268976.2018.1453094
DO - 10.1080/00268976.2018.1453094
M3 - Journal article
VL - 116
SP - 1504
EP - 1511
JO - Molecular Physics
JF - Molecular Physics
SN - 0026-8976
IS - 11
ER -