Band Structure Calculations in HF

Message

tommy91779 · #1 Post by **tommy91779** » Fri Sep 18, 2009 10:03 am

Hello all,

I am attempting to do band structure calculations for bulk GaN in the wurtzite phase using Hartree-Fock in VASP-5.2. I figured the procedure I would follow would be similar to that I followed for DFT: specifiying the appropriate flags in the INCAR ( ICHARG, LORBIT, ISMEAR, SIGMA) and defining high symmetry lines in the KPOINTS file along which I want the band structure computed. However, when I do this I get an error telling me the symmetry I specify that of the underlying crystal. Has anyone performed HF band structure calculations? If so could you provide me with some hints as to where I am going wrong??

Thanks in advance,

Tom

#2 Post by **admin** » Mon Oct 12, 2009 12:23 pm

have you tried to use the KPOINTS file for band structures, specifically? (please see KPOINTS of the vasp-workshop excercise 2-3, for fcc Si , for example)
[ Edited Mon Oct 12 2009, 02:23PM ]

tommy91779 · #3 Post by **tommy91779** » Tue Oct 13, 2009 6:32 pm

Dear admin,

I have adjusted my KPOINTS file to account for the directions along which I wish to plot the band structure. In short I am considering a primitive unit cell of CdSe. I will summarize the procedure I used:

1. Regular DFT Calculation for a n automatically generated MP mesh

2. From this WAVECAR, I run a HF calculation by adjusting the INCAR as depicted in Section 6.64 of the VASP manual.

3. Having obtained a converged calculation, I adjust the INCAR for a band structure calculations. I also modified the KPOINTS file specifically for hexagonal lattice thusly,

k-points along high symmetry lines
10 ! 10 intersections
Line-mode
rec
0.000 0.000 0.500 ! A
0.000 0.500 0.500 ! L

0.000 0.500 0.500 ! L
0.000 0.500 0.000 ! M

0.000 0.500 0.000 ! M
0.000 0.000 0.000 ! Gamma

0.000 0.000 0.000 ! Gamma
0.000 0.000 0.500 ! A

0.000 0.000 0.500 ! A
0.333 0.333 0.500 ! H

0.333 0.333 0.500 ! H
0.333 0.333 0.000 ! K

0.333 0.333 0.000 ! K
0.000 0.000 0.000 ! Gamma

I have tried this with the HF WAVECAR and without. In either case I receive the foloowing error:

running on 8 nodes
distr: one band on 1 nodes, 8 groups
vasp.5.2.2 15Apr09 complex
POSCAR found type information on POSCAR Cd Se
POSCAR found : 2 types and 4 ions
LDA part: xc-table for Ceperly-Alder, standard interpolation
error in IBZKPT_HF: two k-points are equivalent 1 40
this will cause problems in the HF routine

-----------------------------------------------------------------------------
| |
| W W AA RRRRR N N II N N GGGG !!! |
| W W A A R R NN N II NN N G G !!! |
| W W A A R R N N N II N N N G !!! |
| W WW W AAAAAA RRRRR N N N II N N N G GGG ! |
| WW WW A A R R N NN II N NN G G |
| W W A A R R N N II N N GGGG !!! |
| |
| Your generating k-point grid is not commensurate to the symmetry |
| of the lattice. This can cause slow convergence with respect |
| to k-points for HF type calculations |
| suggested SOLUTIONS: |
| ) if not already the case, use automatic k-point generation |
| ) shift your grid to Gamma (G) (e.g. required for hex or fcc lattice) |
| |
-----------------------------------------------------------------------------

error in IBZKPT_HF: two k-points are equivalent 1 40
this will cause problems in the HF routine
error in IBZKPT_HF: two k-points are equivalent 1 40
this will cause problems in the HF routine
error in IBZKPT_HF: two k-points are equivalent 1 40
this will cause problems in the HF routine
error in IBZKPT_HF: two k-points are equivalent 1 40
this will cause problems in the HF routine
error in IBZKPT_HF: two k-points are equivalent 1 40
this will cause problems in the HF routine
error in IBZKPT_HF: two k-points are equivalent 1 40
this will cause problems in the HF routine
error in IBZKPT_HF: two k-points are equivalent 1 40
this will cause problems in the HF routine

Thanks in advance

Tom

VASP001 · #4 Post by **VASP001** » Fri Nov 06, 2009 2:59 am

I have met same the questions.

irene · #5 Post by **irene** » Fri Nov 06, 2009 2:34 pm

I would also like to know.
This problem has been reported in the forum before:
http://cms.mpi.univie.ac.at/vasp-forum/ ... php?4.5664

panda · #6 Post by **panda** » Wed Nov 11, 2009 2:09 am

"1.) Regular DFT Calculation for a n automatically generated MP mesh, followed by:
*****I also modified the KPOINTS file specifically for hexagonal lattice.

You should try to generate a larger n automatic mesh first, it is my guess that you are trying to integrate about a region that is not spanning all the BZ. Also try with ISYM = 0 and see what happens. Cheers and good luck!

gbal · #7 Post by **gbal** » Fri Nov 13, 2009 5:12 pm

I'm also having this same problem when i try to calculate band structure with GW or hybrid functionals. Does any one have another hint or a answer if it is possible or not?
I already tried a bigger K-mesh and it does not work.

kally · #8 Post by **kally** » Mon Nov 16, 2009 6:04 am

defining high symmetry lines in the KPOINTS file along which I want the band structure computed. However, when I do this I get an error telling me the symmetry I specify that of the underlying crystal.

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