Guangping, 2010/4/15 张广平 <[email protected]>
> Dear Marcos, > Thanks for your reply.You mean,the broading width is from the temperature > is not Zero? > Can you please restate your question? I really don't get what you want to know. > KbT is about 0.03eV at room temperature.So the broading width is around the > value KbT,In my calculation ,I usually set the electronic temperature 300K. > You are confusing gaussian broadening for the PDOS with the smearing of the Fermi function, which are two completely different things. It looks like you could use a bit of reading. I am not sure where you could find something about this, maybe Joannopoulos' Reviews of Modern Physics could have something on that. > for quick,I usually set K is 1*1*1,and I set the cell big enough that make > sure the system type is molecular.Because I have found it is much slower if > i use k points.And there is nearly no difference whether you use how many k > points and only Gamma point,when the system type is molecular whether you > use how many k points. > Am I RIGHT，Marcos? > If your intention is to perform a calculation for a molecule or a cluster, definitely this is the thing to do. Marcos > Best wiesh. > 在2010-04-12，"Marcos Veríssimo Alves" <[email protected]> > 写道： > > Guangping, > > There is a difference between the broadening width in the DOS/PDOS > calculated with the ProjectedDensityOfStates block or eig2dos, and the one > you get through interactions of your molecule with some other system > (electrodes, surfaces, clusters, other molecules, whatever). In the first > case, which is what you want to know, it has nothing to do with being an > open or closed system. Rather, the broadening simulates the effect of a > finite temperature on the DOS. if your k-point mesh is sufficiently dense, > the role of the gaussian broadening is to smoothen the DOS. Use physical > wisdom to estimate an initial value for the gaussian broadening: how much is > $k_BT$ at room temperature? Starting from that value, increase and decrease > it value by small amounts: do you see any features that become less evident > as you change the broadening? My rule of thumb is: the "good" broadening is > the lowest which gives you a PDOS that looks sufficiently smooth without > losing any of the peaks or important features. Of course, this is quite > subjective, and changes from system to system. In other words, you have some > flexibility in using the broadening - use it sensibly. > > Marcos > > On Mon, Apr 12, 2010 at 1:59 PM, Guangping Zhang <[email protected]> wrote: > >> Hi,Marcos, >> "peak width" I said means peak width (in eV) for broadening (gaussian or >> lorentzian).Since I get the EIG file,I want to get the DOS ,I must to set >> the broadenin width,So how to define it,for different values have very >> different DOS results.In transiesta,the DOS give automatically.In that >> situation,the system is open ,so there is an interaction between the >> melecular and the electorde,so there is a broadenin width from the >> interaction energy.But if I calculate a isolated molecular,how it comes the >> broadenin width? >> Am I right ? >> Best wishes! >> >> > > > >
