Naslov
Low-Lying ππ* States of Heteroaromatic Molecules: A Challenge for Excited State Methods

Autori
Prlj, Antonio ; Sandoval-Salinas, María Eugenia ; Casanova, David ; Jacquemin, Denis ; Corminboeuf, Clémence

Izvornik
Journal of Chemical Theory and Computation (1549-9618) 12 (2016), 6; 2652-2660

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
density-functional theory, charge-transfer-like, polycyclic aromatic-hydrocarbons, transfer-like excitations, td-dft, basis-sets, polyacenes, benchmarks, spectrum, model

Sažetak
The description of low-lying pi pi* states of linear acenes by standard electronic structure methods is known to be challenging. Here, we broaden the framework of this problem by considering a set of fused heteroaromatic rings and demonstrate that standard electronic structure methods do not provide a balanced description of the two (typically) lowest singlet state (L-a and L-b) excitations. While the L-b state is highly sensitive to correlation effects, L-a suffers from the same drawbacks as charge transfer excitations. We show that the comparison between CIS/CIS(D) can serve as a diagnostic for detecting the two problematic excited states. Standard TD-DFT and even its spin-flip variant lead to inaccurate excitation energies and interstate gaps, with only a double hybrid functional performing somewhat better. The complication inherent to a balanced description of these states is so important that even CC2 and ADC(2) do not necessarily match the ADC(3) reference.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA