The Charge Transfer Problem in Density Functional Theory Calculations of Aqueously Solvated Molecules

Recent advances in algorithms and computational hardware have enabled the calculation of excited states with time-dependent density functional theory (TDDFT) for large systems of O(1000) atoms. Unfortunately, the aqueous charge transfer problem in TDDFT (whereby many spuriously low-lying charge tran...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2013-10, Vol.117 (40), p.12189-12201
Main Authors: Isborn, Christine M, Mar, Brendan D, Curchod, Basile F. E, Tavernelli, Ivano, Martínez, Todd J
Format: Article
Language:English
Subjects:
Algorithms
Atomic and molecular physics
Charge transfer
Coumaric Acids - chemistry
Demand
Density functional theory
Electron correlation calculations for atoms and molecules
Electronic structure of atoms, molecules and their ions: theory
Exact sciences and technology
Excitation
Ground state
Hydrogen Bonding
Mathematical models
Models, Molecular
Oxazines - chemistry
Physics
Propionates
Quantum Theory
Rest
Solvents - chemistry
Water - chemistry
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Summary:Recent advances in algorithms and computational hardware have enabled the calculation of excited states with time-dependent density functional theory (TDDFT) for large systems of O(1000) atoms. Unfortunately, the aqueous charge transfer problem in TDDFT (whereby many spuriously low-lying charge transfer excited states are predicted) seems to become more severe as the system size is increased. In this work, we concentrate on the common case where a chromophore is embedded in aqueous solvent. We examine the role of exchange-correlation functionals, basis set effects, ground state geometries, and the treatment of the external environment in order to assess the root cause of this problem. We conclude that the problem rests largely on water molecules at the boundary of a finite cluster model, i.e., “edge waters.” We also demonstrate how the TDDFT problem can be related directly to ground state problems. These findings demand caution in the commonly employed strategy that rests on “snapshot” cutout geometries taken from ground state dynamics with molecular mechanics. We also find that the problem is largely ameliorated when the range-separated hybrid functional LC-ωPBEh is used.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp4058274