I'm not familiar with SIESTA, but in case some electrons might contribute to the interested energy range, however they are too expensive to consider explicitly, like the d wlwcteons of noble metals. Phenomenological description is an approximation. This is what I meant.
On Tuesday, April 28, 2015, Guangping Zhang <[email protected]> wrote: > Dear Pu Zhang, > > As far as I know, the Drude term in SIESTA is omega_p*omega_p, and the > Drude contribution to the dielectric function is added by the simple Drude > model, > > -omega_p*omega_p/omega/(omega+i*gamma) > > where i is the imaginary unit. Therefore, Drude term used in SIESTA is to > account for the effect of the free electrons. However, for cluster in > SIESTA, all the transitions from occupied to unoccupied orbitals are taken > into account in the interested energy range. I think this would include the > 'free electrons' and the 'bound electrons' in the energy range in the > current framework in SIESTA. > > So, what do you mean by "a contribution from deeper transitions", could > you please give more information on this? > > > /Guangping > > > On 04/27/2015 05:11 PM, Pu ZHANG wrote: > > I suppose the so-called intraband contribution is just the part of the > permittivity which is not described by the simple Drude model. Then it > doesn't necessarily apply to bulk material. For cluster it can also get > contribution from deeper transitions. I guess it's possible to implement > this somehow... > > Best regards, Pu Zhang > -- > Faculty at School of Physics, Huazhong University of Science and > Technology > Room 819 (N.), Yifu Science and Technology Building > 1037 Luoyu Road, Wuhan, China > E-mail: [email protected] > <javascript:_e(%7B%7D,'cvml','[email protected]');> > Homepage: www.researchgate.net/profile/Pu_Zhang4 > Phone: +86 18871860394 > > On Mon, Apr 27, 2015 at 9:34 PM, Guangping Zhang <[email protected] > <javascript:_e(%7B%7D,'cvml','[email protected]');>> wrote: > >> Dear Eliya, >> >> For a cluster, I think there is no energy bands, therefore no intraband >> transition. >> >> /Guangping >> >> On 2015/4/27 14:43, Eliya Asmani wrote: >> >> Dear Guangping >> >> Thanks for the your quick reply. >> As I know the intarband transition (Drude term) is very important for my >> case. >> I'm so sorry! What is your mean about "Drude term is only for a system >> with at least one dimension periodical" you mean the Siesta code can't >> calculate for cluster system or Drude term is not important in cluster >> system? >> >> Eliya >> >> On Mon, Apr 27, 2015 at 4:21 PM, Guangping Zhang <[email protected] >> <javascript:_e(%7B%7D,'cvml','[email protected]');>> wrote: >> >>> Dear Eliya, >>> >>> I think you do not need to include the Durde term for a cluster >>> calculation. The Drude term is only available for a system with at least >>> one dimension periodical. >>> >>> Kind regards, >>> >>> /Guangping >>> >>> On 04/27/2015 12:44 PM, Eliya Asmani wrote: >>> >>> Dear user >>> >>> I want to calculate real and imaginary parts of the permittivity for >>> some metals >>> (for cluster not bulk). >>> How can I include Drude term for intarband transition of the >>> permittivity? >>> >>> In the *.EPSIMG, (was generated after optical calculation) the value >>> of W_p is written 0.000. I think this value should be non-zero, to include >>> Drude term. >>> How can I determinate W_p? >>> >>> Regards, >>> Eliya >>> >>> >>> >> >> > > -- Best regards, Pu Zhang -- Faculty at School of Physics, Huazhong University of Science and Technology Room 819 (N.), Yifu Science and Technology Building 1037 Luoyu Road, Wuhan, China E-mail: [email protected] <[email protected]> Homepage: www.researchgate.net/profile/Pu_Zhang4 Phone: +86 18871860394
