TY  - JOUR
A1  - Bois, Juliana
A1  - Körzdörfer, Thomas
T1  - 0 How Bond Length Alternation and Thermal Disorder Affect the Optical
Excitation Energies of pi-Conjugated Chains: A Combined Density
Functional Theory and Molecular Dynamics Study
JF  - Journal of chemical theory and computation
N2  - We dissect the sources of error leading to inaccuracies in the description of the geometry and optical excitation energies of pi-conjugated polymers. While the ground-state bond length alternation is shown to be badly reproduced by standard functionals, the recently adapted functionals PBEh* and omega PBE* as well as the double hybrid functional XYGJ-OS manage to replicate results obtained at the CCSD(T) level. By analysis of the bond length alternation in the excited state, a sensitive dependence of the exciton localization on the long-range behavior of the functional and the amount of Hartree-Fock exchange present is shown. Introducing thermal disorder through molecular dynamics simulations allows the consideration of a range of thermally accessible configurations of each oligomer, including trans to cis rotations, which break the conjugation of the backbone. Thermal disorder has a considerable effect when combined with functionals that overestimate the delocalization of the excitation, such as B3LYP. For functionals with a larger amount of exact exchange such as our PBEh* and omega PBE*, however, the effect is small, as excitations are often localized enough to fit between twists in the chain.
Y1  - 2016
U6  - https://doi.org/10.1021/acs.jctc.5b01070
SN  - 1549-9618
SN  - 1549-9626
VL  - 12
SP  - 1872
EP  - 1882
PB  - American Chemical Society
CY  - Washington
ER  -