Thanks for your patience.I will read Joannopoulos' Reviews of Modern Physics . Thanks. Best wishes. ------------------ Original ------------------ From: "Marcos Veríssimo Alves"<[email protected]>; Date: Fri, Apr 16, 2010 00:48 AM To: "siesta-l"<[email protected]>; Subject: Re: Re: [SIESTA-L] How to define the peak width in eig2dos !
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!
