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Charge transfer excitations in TDDFT: A ghost‐hunter index
Author(s) -
Campetella Marco,
Maschietto Federica,
Frisch Mike J.,
Scalmani Giovanni,
Ciofini Ilaria,
Adamo Carlo
Publication year - 2017
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.24862
Subject(s) - intramolecular force , intermolecular force , delocalized electron , time dependent density functional theory , ionization energy , physics , charge (physics) , density functional theory , ionization , robustness (evolution) , atomic physics , statistical physics , chemistry , molecular physics , computational chemistry , quantum mechanics , molecule , ion , biochemistry , gene
This work presents a new index, M AC , enabling the on‐the‐fly detection of ghost charge transfer (CT) states, a major problem in time‐dependent density‐functional theory calculations. This computationally inexpensive index, derived as a modification of the Mulliken estimation of transition energy for CT excitations, relies on two basic ingredients: an effective CT distance, computed using our density‐based index ( D CT ), and an orbital weighted estimation of the Ionization Potential and Electron Affinity. Some model systems, representative of both intermolecular and intramolecular CT excitations, were chosen as test cases. The robustness of our approach was verified by analyzing the behavior of functionals belonging to different classes (GGA, global hybrids and range separated hybrids). The results obtained show that ghost states are correctly spotted, also in the delicate case of intramolecular excitations displaying substantial donor‐bridge‐acceptor delocalization, in a regime for which the standard Mulliken formulation attends its limits. © 2017 Wiley Periodicals, Inc.