There is some controversia about the physics meaning of Kohn-Sham
ortibals, i.e. Koopman's theorem is no sastified. However, Perdew, using
Janak's theorem has proven a connection between IPs / EAs and HOMO /
LUMO energies, respectively
P. Perdew, in: R.M. Dreizler, J. Providenca (Eds.), Density
FunctionalMethods in Physics, Plenum Press, New York and London, 1985,
E. Jansson, P. C. Jha, H. Ågren, Chem. Phys. 330, 166, 2006.).
Furthermore, it is known that long-range corrected functionals give
accurate orbital energies and satisfy Koopman theorem.
Tsuneda, T.; Song, J. W.; Suzuki, S.; Hirao, K. J. Chem. Phys., 2010,
133, 174101. **
Rienstra-Kiracofe, J. C.; Tschumper, G. S.; Schaefer, H. F.; Nandi, S.;
Ellison, G. B. Chem. Rev. 2002, 102, 231-282.
Jacquemin, D.; Adamo, Carlo, J. Chem. Theory Comput, 2011, 7, 369-376.
JacJCTC08. D. Jacquemin, E. A. Perpète, G. E. Scuseria, I. Ciofini, C.
Adamo, J. Chem. Theory Comput., 2008, 4, 123.WonJCTC10. b.
Wong, T. H. Hsieh, J. Chem. Theory. Comput, 2010, 6, 3704.JacJCP07. D.
Jacquemin, E. A. Perpète, G. Scalmani, M. J. Frisch, R. Kobayashi,
C. Adamo, J. Chem. Phys., 2007, 126, 144101.
Y. Tawada, T. Tsuneda, S. Yanagisawa, T. Yanai, and K. Hirao, "A
long-range-corrected time-dependent density functional theory," /J.
Chem. Phys./, *120* (2004) 8425.
Sorry, perhaps we are moving away from the Caqhero's problem
El 3/4/2011 11:08 AM, N H escribió:
Well ... for sure there are lots of studies using DFT to calculate
such properties. Another question is whether this results are
meaningful or not... and that is controversial.
The problem is that some people don´t see much meaning on conduction
bands calculated with single reference methods, since their
eigenvalues are not really taken into account while diagonalizing the
system's Hamiltonian.
Another issue is the meaning of the Kohn-Sham orbitals themselves. It
has been demonstrated - at least for molecules - that they do have the
same simmetry properties as HF orbitals and that the also agree with
the Koopman's theorem after rescalling. I also know that there are
some recent works (see the link) on a DFT version of the Koopman's
theorem, but in order to verify that you have to go beyond standard DFT:
http://www.ingentaconnect.com/content/nrc/cjc/2009/00000087/00000010/art00014
Given that, you can calculate the optical properties of any material
with DFT if you think that the conduction bands are meaningful ... but
you are going to have a hard time if your referee think it is not true.
Cheers
NH
2011/3/4 Gregorio García Moreno <[email protected]
<mailto:[email protected]>>
Hi
I have never used SIESTA to calculate optical properties, but
recently have accepted a propious work where electronic structure
of conducting polymers: band diagrams, bandgap, bandwiths,
effective mass, ect. All these properties are related with optical
properties, and the reviewers didn't say anything about the
methodology (DFT and SIESTA)
I can't help you, but you can look for other works where DFT
implemented in siesta is used to assess optical properties.
Besides, respect to DFT there are a lot of works which use DFT to
calculate optical properties of photovoltaic cells, oleds,
synthetized dyes, etc.
I think that that all works of nowadays on optical properties use DFT.
I know that Carlo Adamo's group are working in the development of
new fuctionals to assess optical properties.
Unfortunately, all these functional are not implemented in SIESTA.
On the other hand, there are a lot of scale factors in
bibliography to correct theoretical values in concordance with
experimental ones.
Sorry, I can't help more
Gregorio
El 3/4/2011 9:16 AM, caqhero escribió:
Recently, I used the siesta to calculate the optical properties
of CNTs. The reviewer ask the method I used. and he say that the
Ground-state DFT can not accurately describe optical
properties. I confuse the method for optical calculation in
siesta. can any body tell me the details ? how can I reply
the reviewer ? is it reliable using the siesta to calculate the
optical properties ? any suggestion is appreciated ! thank you !
