Open AccessElectronic Energy Gaps for π-Conjugated Oligomers and Polymers Calculated with Density Functional Theory
Author(s) -
Haitao Sun,
Jochen Autschbach
Publication year - 2014
Publication title -
journal of chemical theory and computation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.001
H-Index - 185
eISSN - 1549-9626
pISSN - 1549-9618
DOI - 10.1021/ct4009975
Subject(s) - observable , density functional theory , band gap , excitation , conjugated system , singlet state , ionization energy , range (aeronautics) , electronic structure , molecular physics , electron affinity (data page) , hybrid functional , materials science , atomic physics , ionization , physics , chemical physics , polymer , chemistry , computational chemistry , condensed matter physics , quantum mechanics , excited state , molecule , ion , composite material
In varying contexts, the terms "energy gap" (energy difference) or "band gap" may refer to different experimentally observable quantities or to calculated values that may or may not represent observable quantities. This work discusses various issues related to calculations of electronic energy gaps for organic π-conjugated oligomers and linear polymers by density functional theory (DFT). Numerical examples are provided, juxtaposing systematic versus fortuitous agreement of orbital energy gaps with observable fundamental (ionization vs electron attachment) or optical (electronic excitation) energy gaps. Successful applications of DFT using nonempirically tuned hybrid density functionals with range-separated exchange (RSE) for calculations of optical gaps, fundamental gaps, and electron attachment/detachment energies are demonstrated. The extent of "charge-transfer like" character in the longest-wavelength singlet electronic excitations is investigated.