Premium
Application of time‐dependent density‐functional theory to electron—ion coupling in ethylene
Author(s) -
Bertsch George F.,
Giansiracusa Jeffrey,
Yabana Kazuhiro
Publication year - 2003
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1560/jjhk-acm8-2e6m-dk9c
Subject(s) - time dependent density functional theory , chemistry , density functional theory , atomic physics , coupling (piping) , excited state , rydberg formula , asymmetry , electron , electron density , molecular physics , ion , physics , ionization , quantum mechanics , computational chemistry , mechanical engineering , organic chemistry , engineering
To examine the applicability of the time‐dependent density‐functional theory (TDDFT) for treating the electron–nucleus coupling in excited states, we calculate the strength distribution associated with the π–π* transition in ethylene. The observed optical transition strength in the 7–8.5 eV region shows a complex structure arising from coupling to C–C stretch motion, to torsional motion, and to Rydberg excitations. The mean energy of the observed peak is reproduced to about 0.2 eV accuracy by the TDDFT in the local density approximation (LDA). The reflection approximation is used to calculate the peak broadening. Roughly half of the broadening can be attributed to the fluctuation in the C–C coordinate. The asymmetry in the line shape is also qualitatively reproduced by the C–C coordinate fluctuation. We find, in agreement with other theoretical studies, that the torsional motion is responsible for the progression of weak transition strength extending from the peak down to about 6 eV. The LDA reproduces the strength in this region to a factor of about 3. We conclude that the TDDFT is rather promising for calculating the electron–nucleus coupling at short times.