Hi all,
My present problem is about the TDDFT with B3LYP
functional and conjugated polymer. I did some investigate on some derivations of
pyrrole and thiophene oligomers using TDDFT with B3LYP functional. The band
gaps(transition energy from the ground state to the first dipole-allowed excited
state) of the corresponding polymers obtained by oligomer extrapolation are in
good agreement with the experimental data within 0.15ev. But the conventional
functionals are local(the potential is a function of the local density or the
local gradient) and are not suited to describe delocalized features. This can
lead to severe errors in the simulation. (see CHEMPHYSCHEM 2003,3,292) However,
some reports also considered the TDDFT with B3LYP is a relatively reliable tool
for evaluating of the transition energies of low-lying excited states.(J
Phys.Chem.A 2001,105,451; J Chem. Phys. 1998,108(11),4439) Now I want to know
why the TDDFT/B3lyp does not suffer from the drawbacks of
local approximations to describe the ultranonlocal features. Thank you
very much!
Sincerely yours,
Su Xing
zzxccl{at}yahoo.com