Dear Shamsu
Your input file and parameters are fine. When you plot the DOS you need to shift your Fermi level to zero if you want the gap to show up at zero. Add the line verbosity = 'high' to the control part of your input file and run pw.x again. Then you can grep your output file less scf.out | grep 'Fermi energy' You should get a line that looks like this: the Fermi energy is -1.6709 ev When you plot your DOS, for instance in gnuplot you would now plot plot 'Graph01.dos' ($1-(-1.6709)):2 w l and you should see your plot with the bandgap and dispersion at zero. When you do these calculations the Fermi level will rarely show up at exactly zero. Robert From: pw_forum-bounces at pwscf.org [mailto:pw_forum-boun...@pwscf.org] On Behalf Of Shamsu Abubakar Sent: Wednesday, April 03, 2013 8:23 PM To: pw_forum at pwscf.org Subject: [Pw_forum] Fermi energy reference point shift from 0 to -2 Dear Q.E Users. I have a system of 4x4 graphene supercell, comprising 32 carbon atoms. I sucessfully run all the calculations i.e scf,nscf and other postprocessing such as DOS and PDOS. But the main problem i'm facing currently is on the density of state. Usually, i consider zero to be my fermi reference energy point in my ./dos.x input file, forexample,from -10 and 10 as my Emin and Emax respectivily. For pristine graphene,i expect to always see the dispersion at the zero vicinity, showing a semi metallic behavior, but surprisingly, its always moving away from zero to around -2, in the valence band side which i knew is unsual for pristine graphene. However, when i combine graphene with GaAs nanostructure, most of the interesting properties interms of orbitals contributions (PDOS), also resides on similar point -2. That is some of the contributions that are supposed to be seen at the vicinity of the fermi level, now moved to another point -2. Also, i consider changing the smearing from marzari-vanderbilt to Fermi- Dirac, but similar properties were observed. I decided to consider only 1x1, and 2x2 graphene supercell alone, still similar properties i observed also. In fact, i even consider changing my pseudopotential from pw91 to pbe.rrkjus still no progress. My problem now, i don't know what really causes these shift from 0 to -2. I attached one of my graphene scf input file for your verification and advice. &CONTROL title = 'Graphene monolayer01', prefix = 'Graph01', calculation = 'scf' , restart_mode = 'from_scratch' , outdir = '/home//???/espresso-4.1.2/bin/' , pseudo_dir = '/home//???/???/espresso-4.1.2/upf_files/' , tstress = .true. , tprnfor = .true. , / &SYSTEM ibrav = 4, celldm(1) = 18.59490373, celldm(3) = 1.80, nat = 32, ntyp = 1, ecutwfc = 34.D0 , tot_charge = 0.000000, occupations = 'smearing' , degauss = 0.02 , smearing = 'fermi-dirac' , / &ELECTRONS conv_thr = 1.D-8 , mixing_beta = 0.7D0 , / ATOMIC_SPECIES C 12.00000 C.pw91-van_ak.UPF ATOMIC_POSITIONS (angstrom) C 1.229999657 0.709326753 1.999999753 C 2.459999165 1.419486000 1.999999874 C 3.689999208 0.709327391 1.999999822 C 4.920000000 1.419486496 1.999999944 C 4.920000000 2.839880146 2.000000125 C 6.149999990 3.549976521 1.999999907 C 3.690000010 3.549976521 1.999999907 C 2.459999764 2.839879152 2.000000067 C 6.150000792 0.709327391 1.999999822 C 7.380000835 1.419486000 1.999999874 C 7.380000236 2.839879152 2.000000067 C 8.610000005 3.549975943 1.999999891 C 8.609999654 4.970023341 2.000000208 C 9.840000000 5.680120078 2.000000200 C 7.379999382 5.680120770 2.000000152 C 6.149999800 4.970024086 2.000000150 C 4.920000000 5.680121474 2.000000132 C 3.690000200 4.970024086 2.000000150 C 8.610000343 0.709326753 1.999999753 C 9.840000000 1.419485253 1.999999874 C 9.840000000 2.839878353 2.000000070 C 11.069999995 3.549975943 1.999999891 C 11.070000346 4.970023341 2.000000208 C 12.300000618 5.680120770 2.000000152 C 12.300001137 7.100514050 2.000000166 C 13.530000464 7.810673002 1.999999744 C 11.070000830 7.810672948 1.999999928 C 9.840000000 7.100514025 2.000000287 C 8.609999170 7.810672948 1.999999928 C 7.379998863 7.100514050 2.000000166 C 6.149999536 7.810673002 1.999999744 C 4.920000000 7.100514261 2.000000041 K_POINTS automatic 6 6 1 0 0 0 Thank you for your kind response. Shamsu Abubakar Postgraduate student Department of Physics University Putra Malaysia -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20130404/fab0ca31/attachment.html