thank you very much Prof. Blaha and Pavel, Prof. Blaha: Yes, in the paper author reported the sharp peal for lowest exciton transition using BSE theory.
Prof. Pavel: I do not have any experience about BSE calculations so for now I want to bindup the project with DFT only. I have finished the calculation with -SO now and the shape of the absorption spectra has changes significantly. The experimental band gap of the compound is 1.62 eV and I am getting it 1.1 eV with SO. In the revised absorption coefficient calculated from Wien2k <https://docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxkZnRmYXRpbWE1fGd4OjZiOGYyYTI3MGQ5N2RjMjk>, the absorption peak starts from ~1.0 eV followed by a shoulder like shape at ~3.eV. In many literature paper, people reported a small broad peak around 1.7 eV and then at ~2.5eV. If I do a tau plot then the onsite absorption edge occurs at ~1.7eV. My further queries are: 1. Should I report the tau plot to compare my tau plot peak with the the sharp absorption peak observed in experiment <https://4bd1924d-a-62cb3a1a-s-sites.googlegroups.com/site/dftfatima5/letter/mailing-list-queries/Absorption_coefficient.png?attachauth=ANoY7coNS62dJC53AmGkh7APGKhfUxz_3oOFRqExrGLyrEYsNFNkgZ8pobRnqjX3egrT7v3GI9sDrJAdvpcAao566zH-5Qk2Tw4q9vd3sYB9_tUu7lKV37w0JLbuje82aR3pXjpQ5iHJR595akXSNQXufL91mtvChfV0LJzB0z94VuI17_noK30lQPqiwXmTddqcQkupX-4_FHQtFJ0G6VadIfUExpWfFnVtyOsumMMrzAp6HrLT9YlrIpG7a_LkbFSSW8ff6fS31taZmDQW4VwtDIE5HlV9PA%3D%3D&attredirects=1>. or 2. Is it possible to apply scissors correction so that my broad shoulder like peak may shifts to lower energy side? Thanks and regards Ms. Fatima On Fri, Aug 4, 2017 at 12:10 PM, Pavel Ondračka <pavel.ondra...@email.cz> wrote: > fatima DFT píše v Čt 03. 08. 2017 v 15:50 +0530: > > Dear Users of Wien2k > > > > I want to simulate optical properties of a perovskite compound. > > In the literature people have reported a sharp peak at 1.6 eV while I > > am not getting it. > > Here is the file from literature and here is the file that I got from > > Wien2k. > > Does including -SO in the calculation may effect the shape of the > > absorption curve? > > > > > > Regards > > Fatima > > > Dear Fatima, > > it is hard to tell without the knowledge of the compound, however in > general sharp peaks like this near the absorption edge are usually > caused by excitonic effects, which are not included in the optic > package (it uses just random phase approximation without local field > effects). If you compound is not too complicated and you are skilled > enough, you can try the BSE unsupported package which can calculate the > optical spectra including the excitons to see it helps. Just be warned, > it is unsupported and much less documented than the Wien2k standards. > Moreover, to get even somewhat converged results requires a LOT of CPU > time and a LOT of memory. > > Best regards > Pavel > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: http://www.mail-archive.com/ > email@example.com/index.html >
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