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

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• 作者：Christine M. Isborn ; Brendan D. Mar ; Basile F. E. Curchod ; Ivano Tavernelli ; Todd J. Mart铆nez
• 刊名：Journal of Physical Chemistry B
• 出版年：2013
• 出版时间：October 10, 2013
• 年：2013
• 卷：117
• 期：40
• 页码：12189-12201
• 全文大小：677K
• 年卷期：v.117,no.40(October 10, 2013)
• ISSN：1520-5207

文摘

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., 鈥渆dge waters.鈥?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 鈥渟napshot鈥?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-蠅PBEh is used.