Karim, thank you for the suggestions, I'll try tomorrow and let you know.
R In date 4/3/11 18:40:44, karim rezouali wrote: > Roberto, > > The band structure appears not to be totally correct. Seeing your input > file systlab.fdf, I realized that this curve is obtained under the gamma > point.approximation > > Try to sample the Brillouin zone as follows: > %block kgrid_Monkhorst_Pack > 2 0 0 0.0 > 0 2 0 0.0 > 0 0 2 0.0 > %endblock kgrid_Monkhorst_Pack > > > Optical calculations: > > %block Optical.Mesh > 2 2 2 > %endblock Optical.Mesh > > These changes will make the calculation slightly heavier but that's the > price to pay for something more accurate. > > I have a question regarding the choice of CG for the relaxation of your > structure. In your case, it seems that the use of the molecular dynamics > such as Nose, NPR,..... is more appropriate. > > Hope this helps > > Karim > > > Indirect (band structure attached) > > > > R > > Roberto: > sorry for this question, but are you sure that this band structure > corresponds to your 64-at calculation? I'd expect much more bands > and much less dispersion with 64 at. supercell. > (I did not count the bands per energy interval, though, > so I might be wrong). > Anyway: how does your total DOS look like? > > Best regards > > Andrei Postnikov > > > In date 4/3/11 15:23:46, karim rezouali wrote: > >> Dear, > >> > >> Is the material under study (ie, bulk amorphous silicon) has a direct > >> electronic gap or not? > >> > >> Karim > >> > >> > >> Hello, > >> > >> I calculated the band structure of bulk amorphous silicon (64 atoms > >> tetrahedrically coordinated). I found an HOMO-LUMO band gap of about 0.7 > >> eV. Then I performed the OpticalCalculation, but I have that the > >> resulting > >> imaginary dielectric function has a peak at E<0.7. How is this possible? > >> I > >> expect that each valence-to-conduction transition must be larger than > >> the > >> bang-gap! > >> > >> Roberto
