[Pw_forum] A question on atomic magnetic moments

[Gabriele Sclauzero]

Dear Srijan,

First, why do you post you request within an existing thread that has nothing to do with your problem?

Where is the proof that the final symmetry is different from the initial one?

I believe that the relaxation procedure will keep the same initial symmetry since forces and stress tensor are symmetrized according to it.
I think that you should not pay attention to differences of the order of 10^-9, since there will be always some sort of numerical/roundoff errors in the calculation.


GS

Il giorno 14/feb/2011, alle ore 12.15, Srijan Kumar Saha ha scritto:

>   
>  Dear QE users,
>  
>  QE is able to find the correct symmetry for the input file, added at the end of this email.
>  Here is the proof:
>  48 Sym.Ops. (with inversion). 
> 
>  However, during vc-relax it breaks the symmetry.
>  Proof goes here:
>    0.000000000   0.000000000   0.000000000
>    0.250189867   0.250189867   0.250189867
>    0.000000000   0.250189689   0.250189689
>    0.250189689   0.000000000   0.250189689
>    0.250189689   0.250189689   0.000000000
>    0.500379494   0.000000000   0.000000000
>    0.750569121   0.250189867   0.250189867
>    0.500379494   0.250189728   0.250189728
>    0.750569299   0.000000000   0.250189689
>    0.750569299   0.250189689   0.000000000
>    0.000000000   0.500379494   0.000000000
>    0.250189867   0.750569121   0.250189867
>    0.000000000   0.750569299   0.250189689
>    0.250189728   0.500379494   0.250189728
>    0.250189689   0.750569299   0.000000000
>    0.500379494   0.500379494   0.000000000
>    0.750569121   0.750569121   0.250189867
>    0.500379494   0.750569260   0.250189728
>    0.750569260   0.500379494   0.250189728
>    0.750569299   0.750569299   0.000000000
>    0.000000000   0.000000000   0.500379494
>    0.250189867   0.250189867   0.750569121
>    0.000000000   0.250189689   0.750569299
>    0.250189689   0.000000000   0.750569299
>    0.250189728   0.250189728   0.500379494
>    0.500379494   0.000000000   0.500379494
>    0.750569121   0.250189867   0.750569121
>    0.500379494   0.250189728   0.750569260
>    0.750569299   0.000000000   0.750569299
>    0.750569260   0.250189728   0.500379494
>    0.000000000   0.500379494   0.500379494
>    0.250189867   0.750569121   0.750569121
>    0.000000000   0.750569299   0.750569299
>    0.250189728   0.500379494   0.750569260
>    0.250189728   0.750569260   0.500379494
>    0.500379494   0.500379494   0.500379494
>    0.750569121   0.750569121   0.750569121
>    0.500379494   0.750569260   0.750569260
>    0.750569260   0.500379494   0.750569260
>    0.750569260   0.750569260   0.500379494
> 
> 
>   Is this possible to keep symmetry of the initial system conserved during vc-relax with BFGS ?
>   
>   Input file:
>     &control
>     calculation='vc-relax'
>     restart_mode='from_scratch',
>     prefix='pbmno',
>     tstress = .true.
>     tprnfor = .true.
>     wf_collect=.true.
>     verbosity='high'
>     etot_conv_thr=1.0D-5, 
>     forc_conv_thr=1.0D-4,
>  /
>   &system
>     ibrav =  1,
>     nat = 40,
>     ntyp=3,
>     celldm(1)=20.70
>     nosym=.FALSE.
>     ecutwfc = 30.0,
>         ecutrho = 240.0,
>     occupations='smearing',
>     smearing='fd',
>     degauss=0.005d0,
>     nspin=2
>       starting_magnetization(2)=1.0,
>  /
>  &electrons
>     diagonalization = 'david'
>     conv_thr =  1.0d-9
>     mixing_beta = 0.7
>  /
>  &ions
>  /
>  &cell
>  /
> ATOMIC_SPECIES
>  Pb   1.0        Pb.UPF
>  Mn   1.0       Mn.UPF
>  O     1.0       O.UPF
> ATOMIC_POSITIONS (alat)
> Pb         0.00  0.00  0.00
> Mn         0.25  0.25  0.25
> O          0.00  0.25  0.25
> O          0.25  0.00  0.25
> O          0.25  0.25  0.00
> Pb          0.50  0.00  0.00
> Mn          0.75  0.25  0.25
> O         0.50  0.25  0.25
> O          0.75  0.00  0.25
> O          0.75  0.25  0.00
> Pb          0.00  0.50  0.00
> Mn          0.25  0.75  0.25
> O         0.00  0.75  0.25
> O          0.25  0.50  0.25
> O          0.25  0.75  0.00
> Pb          0.50  0.50  0.00
> Mn          0.75  0.75  0.25
> O         0.50  0.75  0.25
> O          0.75  0.50  0.25
> O          0.75  0.75  0.00
> Pb          0.00  0.00  0.50
> Mn          0.25  0.25  0.75
> O         0.00  0.25  0.75
> O          0.25  0.00  0.75
> O          0.25  0.25  0.50
> Pb          0.50  0.00  0.50
> Mn          0.75  0.25  0.75
> O         0.50  0.25  0.75
> O          0.75  0.00  0.75
> O          0.75  0.25  0.50
> Pb          0.00  0.50  0.50
> Mn          0.25  0.75  0.75
> O         0.00  0.75  0.75
> O          0.25  0.50  0.75
> O          0.25  0.75  0.50
> Pb          0.50  0.50  0.50
> Mn          0.75  0.75  0.75
> O         0.50  0.75  0.75
> O          0.75  0.50  0.75
> O          0.75  0.75  0.50  
> K_POINTS {automatic}
>  2 2 2  0 0 0
> 
> Thanking you and with my best regards,
> Srijan K
> CCMT
> Indian Institute of Science
> India 560012
> 
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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