On 01/23/2014 08:09 PM, Li, Run wrote: > I?m trying to calculate the DOS of graphene, but no matter what > functional and pseudopotential I use, I keep getting DOS=0 about 1.4eV > around Fermi level , even though the bands calculation can get the Dirac > point at K point, showing the conduction band is touching the valence > bands, so graphene is a semi-metal. I used occupation=tetrahedra in the > nscf calculation to calculate DOS, while occupation=smearing to > calculate bands. Should I use occupation= smearing instead? How do I get > a reasonable DOS? (I used a super-cell with one layer of graphene in the > bottom, and enough vacuum. I hope that?s not a problem)
Dear Run, I'm not sure that tetrahedra give a good result in 2D systems, I would try gaussian smearing for the DOS too and see if it makes a difference. On the other hand, what really matters is not the kind of smearing but its amount. To refine the DOS you'll have to use a smaller smearing and increase the number of k-points. In your case, I have the impression that smearing is small enough but you lack k-point. I cannot say more because you forgot to include the input file. You can do a NSCF calculation with a dense grid before the DOS calculation. Finally (I'm not 100% sure about this), the DOS calculation will reuse the k-points that where defined in the previous SCF or NSCF calculation. Hence, doing a band calculation and then the computing the DOS is wrong: the DOS will be computed with the k-points used for the bands. kind regards -- Dr. Lorenzo Paulatto IdR @ IMPMC -- CNRS & Universit? Paris 6 +33 (0)1 44 275 084 / skype: paulatz http://www-int.impmc.upmc.fr/~paulatto/ 23-24/4?16 Bo?te courrier 115, 4 place Jussieu 75252 Paris C?dex 05 -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 2956 bytes Desc: S/MIME Cryptographic Signature Url : http://pwscf.org/pipermail/pw_forum/attachments/20140124/ac553706/attachment.bin
