"Noise" in the density of states

Message

user · #1 Post by **user** » Mon Apr 02, 2007 5:55 am

Dear All,

When we increase the supercell size (say, from 2 atoms/cell to 64 atoms/cell) we usually see lots of fluctuations/noise in the density of states (of the larger supercell), even when we use quite many k-points (tetrahedron method with Bloch corrections, ISMEAR=-5, is used). So this doesn't seem to be related to the number of k-points used in the calculation.

Could you please tell me what are the sources of the noise? And is there any way to reduce it so as we can get the real physics out of the obtained DOS?

Thanks.

#2 Post by **admin** » Mon Apr 02, 2007 8:33 am

what do you mean by "noise"?

user · #3 Post by **user** » Mon Apr 02, 2007 5:52 pm

Dear Admin,

Please click on this link for a figure showing the DOS of supercells with 2 and 64 atoms (same compound).

Thanks.

<span class='smallblacktext'>[ Edited Mon Apr 02 2007, 07:54PM ]</span>

#4 Post by **admin** » Tue Apr 03, 2007 12:57 pm

you seem to have used different setups (smearing width, kmesh densities) for the two plots. Otherwise your 64-atom DOS seems reasonable to me (given that nothing is said about the actual system.)