[Pw_forum] Fractional translations in magnetic system

[Andrea Dal Corso]

On Sun, 2015-02-22 at 13:57 +0300, MKondrin wrote:
> Dear QE users and developers!
> 
> I want to calculate properties of FeS2 (pyrite), space group Pa-3. 
> First, I use non-relativistic pseudopotentials
> 
>  
> ATOMIC_SPECIES
> Fe 55.845 Fe.pw-mt_fhi.UPF
> S 32.066 S.pw-mt_fhi.UPF
> 
> and to make QE properly find all (24) symmetry operations I had to set 
> parameters nr1=100,nr2=100,nr3=100. In this case this trick works.
> 
> However when I try to use relativistic pseudopotentials
> 
> Fe 55.845  Fe.rel-pbe-spn-kjpaw_psl.0.2.1.UPF
> S 32.066 S.rel-pbe-n-kjpaw_psl.0.1.UPF
> 
> with the spin-orbital interaction ( lspinorb=.true., 
> starting_magnetization=0.5, noncolin=.true., however the system should 
> be diamagnetic) I always get in the output file the message

The code discards the symmetries that do not send the starting
magnetization in itself. If you are interested in the nonmagnetic case
do not set a starting_magnetization.

HTH,

Andrea


> 
>  8 Sym. Ops., with inversion, found (18 have fractional translation)
> 
> If nr* parameters weren't set in input file, then the  automatically 
> generated  FFT grid seems quite compatible with fractional translations:
> 
>  Dense  grid:   263859 G-vectors     FFT dimensions: (  80,  80,  80)
> 
>  Smooth grid:    84247 G-vectors     FFT dimensions: (  60,  60,  60)
> 
> Also setting nr1=100,nr2=100,nr3=100 (that is to the same values as in 
> the non-relativistic case) didn't produce any effect. The program didn't 
> find missing symmetry operations.
> 
> I am in a loss. Thank you for your help in advance (input file is 
> attached to the mail).
> 
> 
> Best regards,
> 
> M. V. Kondrin (High Pressure Physics Institute RAS, Troitsk, Russia)
> plain text document attachment (vc.relax.in)
> &control
>     calculation = 'vc-relax',
>     restart_mode='from_scratch',
>     prefix='FeS2',
>     etot_conv_thr=5d-4,
>     forc_conv_thr=5d-3,
>     tstress = .true.,
>     tprnfor = .true.,
>     pseudo_dir = '../pseudo',
>     outdir='./tmp',
>     disk_io='low'
>  /
> &system
>     ibrav=  1, celldm(1) =10.21, nat=  12, ntyp= 2,
>     ecutwfc =70, ecutrho=600.0, occupations='smearing',
>     lspinorb=.true., starting_magnetization=0.5, noncolin=.true.,
>     smearing='methfessel-paxton', degauss=0.02, nr1=100, nr2=100, nr3=100
> /
> &electrons
>     mixing_beta = 0.7
>     conv_thr =  1.0d-4
> /
> &ions
>    upscale=50.0
> /
> &cell
> /
> ATOMIC_SPECIES
> Fe 55.845  Fe.rel-pbe-spn-kjpaw_psl.0.2.1.UPF
> S 32.066 S.rel-pbe-n-kjpaw_psl.0.1.UPF
> ATOMIC_POSITIONS crystal
> Fe 0.0 0.0 0.0
> Fe 0.5 0.5 0.0
> Fe 0.5 0.0 0.5
> Fe 0.0 0.5 0.5
> S 0.389 0.389 0.389
> S 0.889 0.111 0.611
> S 0.611 0.889 0.111
> S 0.111 0.611 0.889
> S 0.611 0.611 0.611
> S 0.111 0.889 0.389
> S 0.389 0.111 0.889
> S 0.889 0.389 0.111
> K_POINTS {automatic}
> 5 5 5 0 0 0
> 
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-- 
Andrea Dal Corso                    Tel. 0039-040-3787428
SISSA, Via Bonomea 265              Fax. 0039-040-3787249
I-34136 Trieste (Italy)             e-mail: dalcorso at sissa.it