Abstract
We identify excitonic confinement in one-dimensional molecular chains (i.e., polyacetylene and ) as the main driving force for the saturation of the chain polarizability as a function of the number of molecular units. This conclusion is based on first principles time-dependent density-functional theory calculations using a recently developed exchange-correlation kernel that accounts for excitonic effects. The failure of simple local and semilocal functionals is shown to be linked to the lack of memory effects, spatial ultranonlocality, and self-interaction corrections. These effects get smaller as the gap reduces, in which case such simple approximations do perform better.
- Received 10 October 2007
DOI:https://doi.org/10.1103/PhysRevLett.101.133002
©2008 American Physical Society