band structure K points?

[Jiaye Li]

Dear all

When I calculated the band structure of a semiconductor surface via vasp, I meet with such problems:"The linear tetrahedron method can not be used with the KPOINTS file, (generation of strings of k-points) " Subsequently, the job failed.

This is my INCAR and KPOINTS:

SYSTEM
Startparameter for this Run:
NWRITE = 2 verbosity write-flag
LPETIM= F write-flag & timer #
ISTART = 0 0-new 1-cont 2-samecut job
ISPIN = 1 1-no, 2-yes
INIWAV = 1 0-jellium WF; 1-random numbers (recomm.)
ICHARG = 11
Electronic Relaxation
! ENCUT = 400.00 #Ecut (eV)
PREC = Medium * #precission: #Low/Medium/High
NELM = 150 max. # of electronic SC steps
NELMDL = 5 # of non-consistent steps at the beggining:>0 or <0
EDIFF = 1.0e-4 stopping-criterion for electronic upd.
VOSKOWN = 1
ISMEAR = -5
SIGMA = 0.1
AMIX = 0.2
BMIX = 0.0001

Ionic relaxation
EDIFFG = 1.0e-3 stopping-conditions for ionic relax.loop (EDIFF*10)
NSW = 0 * # of steps for ionic update (def:0)
IBRION = 2 * ionic relax: -1:no move; 0-MD;1-Newton;2-CG;3-damped;4-?
ISIF = 2 * calc.stress:0-no;1-tr;2-7 yes; 3-change vol.4-change shape
! ISYM = 2 symmetry:0-OFF, 1-ON,2-ON+memory conserving for CD

POTIM = 0.3 if IBRION=1,2,3:scaling constant forces;IBRION=0,time st.


! LPLANE = .TRUE.
! NPAR = 8
! IALGO = 48 * algorithm: use only 8 (CG) or 48 (RMM-DIIS)
LDIAG = .TRUE. sub-space diagonalisation
GGA = 91 * xc-type: PB, PW (86), LM, 91 (Perdew-Wang 91)

LWAVE = .T. * write WAVECAR
LCHARG = .T. * write CHGCAR and CHG
LVTOT = .F. * write the local potential LOCPOT
LELF = .F. create ELFCAR file
LORBIT = .F. create PROOUT
LREAL = auto


Line
10 !10 intersections
Line-mode
cart
0 0 0 !gamma
1 0 0 !X

1 0 0 !X
1 1 0 !M

1 1 0 !M
1 1 1 !R

1 1 1 !R
0 0 0 !gamma


before the above calculation, I performed a SCF calculation using the following KPOINTS:

Silicon !Comment
0 !automatic generation of k-points
Monkhorst !use Monkhorst Pack
3 3 3 !grid 4x4x4
0 0 0 !shift (usually 0 0 0)


I wonder whether the problem lie in "Monkhorst" ? How to choose the correct K points?

Thanks in advance!

[admin]

The error message says what you have to do.... you cannot construct tetrahedra if the k-points are distributed along straight lines. Therefore use a different BZ integration scheme but the tetrahedron method for the band-srtucture run.

[Jiaye Li]

Thank you admin, When I used ISMEAR=0 instead, It worked. But, I used 10 intersections along a line, vasp reported errors: "/opt/mpich/bin/mpirun.ch_shmem: line 91: 2447 Killed " Is it a problem of mpich ?

[Jiaye Li]

I tried to reduce the number of K points to 5, it can run. But 5 k points is too rough. My PC has 4GB memory

[admin]

you are right, 5 kpoints per line is too coarse. Please try if the mesh can be increased, maybe this error is not reproducible.

[Danny]

[quote="Jiaye Li"]I tried to reduce the number of K points to 5, it can run. But 5 k points is too rough. My PC has 4GB memory[/quote]
check how much memory you need per Irreduceble K-point in your static calculation(the number of irreducible kpoints can be found on the second line of the file IBSKPT, the amount of memory you used in your static calculation you probably know from your cluster otherwise grep MB OUTCAR this will give you a lower limit of the total amount of Memory used)

now multiply the number of kpoints(in your example of 10 kpoints per section this is 40) by the amount of memory/Irreducible kpoint, this should be less than 4gb. If your problem is a memory problem this will tell you.
In this case the best thing you van do is split up your bandcalculation(this is nonselfconsistent anyhow) in smaller parts(eg 1 section per calculation) such that you can use 10 or 20 kpoints in this section(if that is within the limits of your memory)

Danny

[Jiaye Li]

Thanks a lot.