[Wien] NON-ZERO forces for zinc-blend GaAs / *.outputnn
Oleg Rubel
oleg.rubel at Physik.Uni-Marburg.de
Mon Mar 12 13:07:39 CET 2007
Additional information: Below I listed information about
nearest-neighbours fron *.outputnn file. It seems that all atoms are
4-coordinated and the bond lengthes are all equal as it should be in the
zinc-blend structure. Nevertheless non-zero forces are observed :-(
Oleg Rubel
marc-hn:~/wien_work/GaAs111APB/4atoms/noAPB> cat noAPB.outputnn
GaAs111APB
R 4
RELA
7.502403 7.502403 36.754118 90.000000 90.000000120.000000
...
ATOM: 1 EQUIV. 1 As1 AT 0.00000 0.00000 0.00000
RMT( 1)=2.00000 AND RMT( 3)=2.00000
SUMS TO 4.00000 LT. NN-DIST= 4.59426
ATOM: 3 Ga1 AT 0.1250 0.1250 0.1250 IS 4.59426 A.U. 2.43118 ANG
ATOM: 4 Ga2 AT -0.3750 -0.3750 0.6250 IS 4.59426 A.U. 2.43118 ANG
ATOM: 4 Ga2 AT -0.3750 0.6250 -0.3750 IS 4.59426 A.U. 2.43118 ANG
ATOM: 4 Ga2 AT 0.6250 -0.3750 -0.3750 IS 4.59426 A.U. 2.43118 ANG
...
ATOM: 2 EQUIV. 1 As2 AT 0.50000 0.50000 0.50000
RMT( 2)=2.00000 AND RMT( 4)=2.00000
SUMS TO 4.00000 LT. NN-DIST= 4.59426
ATOM: 4 Ga2 AT 0.6250 0.6250 0.6250 IS 4.59426 A.U. 2.43118 ANG
ATOM: 3 Ga1 AT 0.1250 0.1250 1.1250 IS 4.59426 A.U. 2.43118 ANG
ATOM: 3 Ga1 AT 0.1250 1.1250 0.1250 IS 4.59426 A.U. 2.43118 ANG
ATOM: 3 Ga1 AT 1.1250 0.1250 0.1250 IS 4.59426 A.U. 2.43118 ANG
...
ATOM: 3 EQUIV. 1 Ga1 AT 0.12500 0.12500 0.12500
RMT( 3)=2.00000 AND RMT( 1)=2.00000
SUMS TO 4.00000 LT. NN-DIST= 4.59426
ATOM: 1 As1 AT 0.0000 0.0000 0.0000 IS 4.59426 A.U. 2.43118 ANG
ATOM: 2 As2 AT -0.5000 0.5000 0.5000 IS 4.59426 A.U. 2.43118 ANG
ATOM: 2 As2 AT 0.5000 -0.5000 0.5000 IS 4.59426 A.U. 2.43118 ANG
ATOM: 2 As2 AT 0.5000 0.5000 -0.5000 IS 4.59426 A.U. 2.43118 ANG
...
ATOM: 4 EQUIV. 1 Ga2 AT 0.62500 0.62500 0.62500
RMT( 4)=2.00000 AND RMT( 2)=2.00000
SUMS TO 4.00000 LT. NN-DIST= 4.59426
ATOM: 2 As2 AT 0.5000 0.5000 0.5000 IS 4.59426 A.U. 2.43118 ANG
ATOM: 1 As1 AT 0.0000 1.0000 1.0000 IS 4.59426 A.U. 2.43118 ANG
ATOM: 1 As1 AT 1.0000 0.0000 1.0000 IS 4.59426 A.U. 2.43118 ANG
ATOM: 1 As1 AT 1.0000 1.0000 0.0000 IS 4.59426 A.U. 2.43118 ANG
...
On Mon, 12 Mar 2007, Stefaan Cottenier wrote:
>
> Did you either use -fc as convergence criterium or did changed TOT to
> FOR manually for the last iteration(s)? If not, then you did not
> calculate the Pulay corrections. Having them as well, should cancel the
> values you have now back to zero.
>
> Note there is a different treatment for positions that cannot have a
> force by symmetry (no :FOR lines are printed at all) and positions that
> can have a force -- which might be 'accidentally' zero (:FOR is printed,
> but you need the FOR keyword to have the complete force here).
>
> AUTHORS : as far as I know, there is no straightforward way to recognize
> afterwards (in files of a saved calculation for instance, which do not
> necessarily include case.in2) whether or not FOR was used. A simple
> remedy would be to print a line before the :FOR/:FGL lines: "Calculated
> with TOT/FOR in case.in2 : (NO) Pulay corrections added"
>
> Stefaan
>
>
> Oleg Rubel wrote:
>
> >Dear Wien2k Users,
> >
> >I met a problem with NON-ZERO forces while performing SCF calculation for
> >a zinc-blend GaAs supercell.
> >
> >
> >Structure: My supercell belongs to a rhombohedral crystal system with 4
> >non-equivalent atoms and the edges along [-1 1 0], [101], and [111]
> >directions (please see the structure file below). (I need this structure
> >for further calculation of {111} antiphase boundaries.) This structure
> >cannot be reduced down to a primitive 2-atom basis due to explicit
> >specifying of Ga and As atoms as non-equivalent (As1, As2, Ga1, Ga2).
> >
> >
> >Problem: When I perform 'run_lapw -ec 0.00005', I do see non-zero forces,
> >though I expect the opposite since the structure is perfect (I verified
> >that by measuring of interatomic distances and angles in XCRYSDEN):
> >
> >marc-hn:~/wien_work/GaAs111APB/4atoms/noAPB> grep :FOR *.scf
> >:FOR001: 1.ATOM 0.699 0.000 0.000 0.699
> >:FOR002: 2.ATOM 0.699 0.000 0.000 0.699
> >:FOR003: 3.ATOM 0.647 0.000 0.000 -0.647
> >:FOR004: 4.ATOM 0.647 0.000 0.000 -0.647
> >:FOR001: 1.ATOM 0.603 0.000 0.000 0.603
> >:FOR002: 2.ATOM 0.603 0.000 0.000 0.603
> >:FOR003: 3.ATOM 0.560 0.000 0.000 -0.560
> >:FOR004: 4.ATOM 0.560 0.000 0.000 -0.560
> >:FOR001: 1.ATOM 0.021 0.000 0.000 0.021
> >:FOR002: 2.ATOM 0.021 0.000 0.000 0.021
> >:FOR003: 3.ATOM 0.013 0.000 0.000 -0.013
> >:FOR004: 4.ATOM 0.013 0.000 0.000 -0.013
> >
> >I also met the similar problem while calculation elastic constants of
> >zinc-blend GaAs using ELAST. It also creates a rhombohedral structure with
> >a 2-atom basis and also gives non-zero forces.
> >
> >There was NO warning messages neither during initialization nor during SCF
> >runs. I also use well approver Rmt radiuses (2.0 for both atoms), safe RKM
> >= 7, and dense k-point mesh (total 1000 k-points in the BZ). Everything
> >runs smoothly and the total energy is converged within several SCF cycles.
> >I do not understand what is wrong?
> >
> >In addition, I verified the structure by setting Ga and As atoms as
> >equivalent. Then wien2k reduces the structure automatically to a 2-atom
> >FCC basis as it should be for the zinc-blend structure, and then
> >everithing is fine: NO forces!
> >
> >
> >Any suggestions and/or comments are highly welcome.
> >
> >Thank you in advance,
> >
> >Yours sincerely,
> >
> >Oleg Rubel
> >
> >===========================
> >Faculty of Physics
> >Philipps University Marburg
> >Renthof 5, 35032 Marburg, Germany
> >E-mail: Oleg.Rubel at physik.uni-marburg.de
> >Homepage: http://www.staff.uni-marburg.de/~rubel/
> >
> >
> >marc-hn:~/wien_work/GaAs111APB/4atoms/noAPB> cat *.struct
> >GaAs111APB
> >R LATTICE,NONEQUIV.ATOMS: 4 160 R3m
> >MODE OF CALC=RELA unit=bohr
> > 7.502403 7.502403 36.754118 90.000000 90.000000120.000000
> >ATOM -1: X=0.00000000 Y=0.00000000 Z=0.00000000
> > MULT= 1 ISPLIT= 4
> >As1 NPT= 781 R0=0.00005000 RMT= 2.0000 Z: 33.0
> >LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> > 0.0000000 1.0000000 0.0000000
> > 0.0000000 0.0000000 1.0000000
> >ATOM -2: X=0.50000000 Y=0.50000000 Z=0.50000000
> > MULT= 1 ISPLIT= 4
> >As2 NPT= 781 R0=0.00005000 RMT= 2.0000 Z: 33.0
> >LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> > 0.0000000 1.0000000 0.0000000
> > 0.0000000 0.0000000 1.0000000
> >ATOM -3: X=0.12500000 Y=0.12500000 Z=0.12500000
> > MULT= 1 ISPLIT= 4
> >Ga1 NPT= 781 R0=0.00005000 RMT= 2.0000 Z: 31.0
> >LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> > 0.0000000 1.0000000 0.0000000
> > 0.0000000 0.0000000 1.0000000
> >ATOM -4: X=0.62500000 Y=0.62500000 Z=0.62500000
> > MULT= 1 ISPLIT= 4
> >Ga2 NPT= 781 R0=0.00005000 RMT= 2.0000 Z: 31.0
> >LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> > 0.0000000 1.0000000 0.0000000
> > 0.0000000 0.0000000 1.0000000
> > 6 NUMBER OF SYMMETRY OPERATIONS
> > 1 0 0 0.0000000
> > 0 1 0 0.0000000
> > 0 0 1 0.0000000
> > 1
> > 0 0 1 0.0000000
> > 1 0 0 0.0000000
> > 0 1 0 0.0000000
> > 2
> > 0 1 0 0.0000000
> > 0 0 1 0.0000000
> > 1 0 0 0.0000000
> > 3
> > 0 1 0 0.0000000
> > 1 0 0 0.0000000
> > 0 0 1 0.0000000
> > 4
> > 1 0 0 0.0000000
> > 0 0 1 0.0000000
> > 0 1 0 0.0000000
> > 5
> > 0 0 1 0.0000000
> > 0 1 0 0.0000000
> > 1 0 0 0.0000000
> > 6
> >
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