Zahra, When you calculated DOS with SIESTA, what method did you use? Did you use EIG2DOS or did you use a PDOS utility (then sum the PDOS on each atom and orbital), or something else?
I would trust your 'band' energy diagrams for this molecule. The DOS calculation uses a Gaussian smearing parameter that you set yourself. If the HOMO-LUMO gap around the Fermi energy is close to your smearing parameter, what you show in the DOS you shared will happen. Try lowering the value for the smearing parameter (According to your plots it looks like it is around 0.250). If you used eig2dos with a first line like this: -3.4561 0.25 1000 -10 10 reduce the second number to something less than, about 0.05. How you would plot a DOS curve is something of a personal preference, considering clarity and value of information presented. A smaller smearing width will change how the curve looks somewhat. Change the parameters until you get something you are satisfied with. Also, using many k-points when calculating an isolated molecule is not usually a good idea. Use a 1x1x1 k-point mesh for a molecule and only worry about convergence with respect to the real space mesh cutoff. Best of Luck, Abraham Hmiel Katherine Belz Groves Fellow in Nanoscience Xue Group, College of Nanoscale Science and Engineering at SUNY Albany On Mon, Oct 10, 2011 at 8:45 AM, Zahra Talebi <[email protected]>wrote: > hi dear siesta usrs, > t first I hope to be able to ask my question in a right way, because my > english isnot good. > I just did some run and got the result as band structure and dos for the > special run of siesta. As you notic I attached them to my e-mail. my band > structure showes a very smal band gap arround gama and because I am running > for molecule, the band structure must be the same in other path of beriloan > zone too, by such a band strucute I expect to see a very small gap in my DOS > arrround fermi energy but not only I don`t have any gap there is a tick > near fermi energy. can any body tell me why this happen. if you need my fdf > I can send it for you. > also I have some other run too which Ihave the same problem for them. I > mean I have a gap arround fermi energy in my band structure but in my DOS > diagram I can see the DENSITy arround the frmi energy. > Thanks for your help. > >
