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Molecular excited states from the SCAN functional

Research output: Contribution to journalJournal article

E-pub ahead of print
<mark>Journal publication date</mark>8/04/2018
<mark>Journal</mark>Molecular Physics
Number of pages8
<mark>State</mark>E-pub ahead of print
Early online date8/04/18
<mark>Original language</mark>English


The performance of the strongly constrained and appropriately normed (SCAN) [Phys. Rev. Lett.
115, 036402 (2015)] meta-generalised gradient approximation exchange–correlation functional is
investigated for the calculation of time-dependent density-functional theory (TDDFT) molecular
excitation 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. For
local excitations, SCAN can exhibit significant triplet instability problems, resulting in imaginary
triplet 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 future
functional development.

Bibliographic note

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