At first thanks for the references Gregorio!!
:) Some of them I really dont know until now!
The question I alwaus rise on this issue is that, sure, the electronic
density derived from the Kohn-Sham orbitals do have the information
about all electronic states for a given system in a given external
potential. But, as most refereces you already cited above, to extract
this information it is necessary to go beyond the time-independet
approach. And that is were the discussion comes back to the caqhero
question. There might be particular TD siesta implementations ... but
they are particular!
Concerning on the relation between IPs/EAs and HOMO/LUMO ... sure, you
are absolutely right. But this LUMO just assumes a physical meaning if
you are putting one electron there and calculating the EA. Otherwise,
this orbital will never be taken into account while minimizing the
electronic energy.
Caqhero
To be brief ... the official SIESTA package is not an implementation
of Time-Dependent DFT. :(
Cheers
NH
2011/3/4 Gregorio García Moreno <[email protected]
<mailto:[email protected]>>
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 !
