Dear Nazma , Thank you very much for your clarification and for giving me a reference on optical properties.
2009/10/31 Nazma Ikram <nazmaikram at hotmail.com> > Please be clear about two things: > 1. Electrons > 2.Photons. > > When we talk about optical properties such as transparent, reflecting or > an opaque material ,we are talking about those photons which correspond to > the optical region of the spectrum. > > When we consider electronic conduction, we are talking about electrons. > > When we calculate the band structure of a crystalline solid, we get regions > of electron energy separated by energy gaps which arise due to the > periodicity of the crystal. > > We can excite an electron from the valence band to the conduction band in > a semiconductor by bombarding photons on the crystal such that these photons > have energy larger than the band gap. That is we have photoconductivity. > > If you look at the mathematical expression for electronic conductivity, you > will find that there is 'difference of the gradient of energyof the > conduction & the valence band' in the denominator.When these two gradients > are equal, there is resonance & hence a peak. > > Read the first few chapters of the book on 'The optical properties of > solids' by FOX. It has simple mathematics & gives clear concepts. > > All the best. > > > ------------------------------ > Date: Fri, 30 Oct 2009 22:18:55 +0530 > > From: shamikphy at gmail.com > To: wien at zeus.theochem.tuwien.ac.at > Subject: Re: [Wien] optical conductivity or electronic conductivity? > > > Dear Nazma, > > Thank you very much for your reply. To further clarify > my doubt I am asking one more question. If we get one peak in the optical > (i.e. electronic) conductivity spectrum does it mean that at that frequency > more photons will be absorbed giving high value of its absorbtance and also > high value of electronic conductivity i.e. does it mean at that frequency > the material is electronically conducting (transparent) but optically > opaque?... > > Shamik Chakrabarti > > 2009/10/30 Nazma Ikram <nazmaikram at hotmail.com> > > > The word optical here means that e m radiations in the frequency range > corresponding to optical spectum are incident on the semiconductor, causing > transition of electrons (hence electronic) from the valence to conduction > band. > ------------------------------ > Date: Thu, 29 Oct 2009 10:26:29 +0530 > From: shamikphy at gmail.com > To: wien at zeus.theochem.tuwien.ac.at > Subject: [Wien] optical conductivity or electronic conductivity? > > > Dear wien2k users, > > By calculating dielectric tensor we can calculate electronic > conductivity. I have calculated dielectric tensor and from which I have also > deduced electronic conductivity sigma by following the relation: > > Im.epsilon=sigma/omega > > where sigma=electronic conductivity > and omega=angular frequency of the EM wave (energy*2pi/h) > > Now In file case.absorpup (or dn) we can find the data for optical > conductivity in unit 1/(ohm.cm). But when I plot optical and electronic > conductivity separately I have found they are exactly the same. Then my > question is > > Q: whether we find optical or electronic conductivity in the file > case.absorpup? > > P.S. optical and electronic conductivity are not the same thing!...glass is > electronically insulating but optically conducting (transparent) material. > > ------------------------------ > Windows 7: I wanted more reliable, now it's more reliable. > Wow!<http://microsoft.com/windows/windows-7/default.aspx?h=myidea?ocid=PID24727::T:WLMTAGL:ON:WL:en-US:WWL_WIN_myidea:102009> > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > > > > ------------------------------ > Windows 7: I wanted more reliable, now it's more reliable. > Wow!<http://microsoft.com/windows/windows-7/default.aspx?h=myidea?ocid=PID24727::T:WLMTAGL:ON:WL:en-US:WWL_WIN_myidea:102009> > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20091031/26319a0c/attachment.htm>