[Pw_forum] RE : Noncolin vs Nspin=1 for Chromium

[Ben Palmer]

Hi Cyrille,

I completely forgot about declaring the second atom.  I will try it 
again with the starting magnetizations you have suggested, and I will 
declare the second atom this time.  I will also turn off lspinorbit.

Thank you again for your help.

All the best,

Ben

> You can only use lspinorbit=.true. if you have a relativistic pseudo which not the case of my pseudo...
> In any case I do not think spin-orbit coupling will change very much your bulk modulus.
> SOC is just a tiny effect on total energy, at least for 3d metals...
>
> The most important thing is that you describe properly the AF state. Why do you initialize the magnetization with
> starting_magnetization(1)=0.7,
> starting_magnetization(2)=-0.4,
> breaking the symmetry between the two atoms.
> Furthermore you have declared only one type of atoms while you have two types..
> I guess you will endup with the non-magnetic solution in your case..
>
> You should declare ntype=2
> and
> starting_magnetization(1)=0.3,
> starting_magnetization(2)=-0.3,
>
>
> hth
> cyrille
>
> -----------------------------------------------------------------------------------------------------------
> Cyrille Barreteau
> CEA Saclay, IRAMIS, SPCSI, Bat. 462
> 91191 Gif sur Yvette Cedex, FRANCE
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> phone:    +33 (0)1 69 08 29 51 / +33 (0)6 47 53 66 52
> fax :       +33 (0)1 69 08 84 46
> email:     cyrille.barreteau at cea.fr
> Web:     http://iramis.cea.fr/Pisp/cyrille.barreteau/
>   -----------------------------------------------------------------------------------------------------------
>
> ________________________________________
> De : pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] de la part de Ben Palmer [benpalmer1983 at gmail.com]
> Date d'envoi : jeudi 6 juin 2013 18:27
> À : PWSCF Forum
> Objet : [Pw_forum] Noncolin vs Nspin=1 for Chromium
>
> Hi Everyone,
>
> I've been using a few of the supplied PPs and one kindly suggested/sent
> to me by Derek/Cyrille.  I've used these to try to calculate the bulk
> modulus.  First, I used nspin = 1 and with the latest PP ended with a
> bulk modulus of 268GPa.  I then repeated with noncolin=.true. and
> lspinorb=.true. and I was expecting a different result, but at the end
> it gave me 268GPa again.  I was just wondering whether I'd missed
> something in my input script, or whether I'd made any obvious errors?
>
> This is one of my nspin=1 input files:
>
> &CONTROL
> restart_mode='from_scratch',
> calculation=scf,
> etot_conv_thr=1.0E-7,
> forc_conv_thr=1.0D-6,
> nstep=200,
> prefix="7ca5bad5d48c",
> pseudo_dir="/gpfs/bb/bxp912/pseudopotentials/",
> outdir="/gpfs/bb/bxp912/scratch/",
> /
> &SYSTEM
> ibrav=14,
> celldm(1)=5.36800113,
> celldm(2)=1,
> celldm(3)=1,
> celldm(4)=0,
> celldm(5)=0,
> celldm(6)=0,
> nat=2,
> ntyp=1,
> ecutwfc=600,
> ecutrho=2400,
> occupations='smearing',
> smearing='mv',
> degauss=0.1,
> /
> &ELECTRONS
> diagonalization='david',
> mixing_mode='plain',
> mixing_beta=0.7,
> conv_thr=1.0D-7,
> /
> &IONS
> ion_dynamics='bfgs',
> /
> &CELL
> cell_dynamics='bfgs',
> press=0.0,
> cell_factor=2.0,
> /
> ATOMIC_SPECIES
> Cr 51.9961 Cr.pbe-us_norel_cyrille.UPF
> ATOMIC_POSITIONS crystal
> Cr 0.0000000000 0.0000000000 0.0000000000
> Cr 0.5000000000 0.5000000000 0.5000000000
> K_POINTS automatic
> 8 8 8 1 1 1
>
> And this is one of my noncolin input files:
>
> &CONTROL
> restart_mode='from_scratch',
> calculation=scf,
> etot_conv_thr=1.0E-7,
> forc_conv_thr=1.0D-6,
> nstep=200,
> prefix="c7700ccaacf",
> pseudo_dir="/gpfs/bb/bxp912/pseudopotentials/",
> outdir="/gpfs/bb/bxp912/scratch/",
> /
> &SYSTEM
> ibrav=14,
> celldm(1)=5.4753116928,
> celldm(2)=1,
> celldm(3)=1,
> celldm(4)=0,
> celldm(5)=0,
> celldm(6)=0,
> nat=2,
> ntyp=1,
> ecutwfc=400,
> ecutrho=1200,
> occupations='smearing',
> smearing='mv',
> degauss=0.1,
> noncolin=.true.,
> lspinorb=.true.,
> starting_magnetization(1)=0.7,
> starting_magnetization(2)=-0.4,
> /
> &ELECTRONS
> diagonalization='david',
> mixing_mode='plain',
> mixing_beta=0.7,
> conv_thr=1.0D-7,
> /
> &IONS
> ion_dynamics='bfgs',
> /
> &CELL
> cell_dynamics='bfgs',
> press=0.0,
> cell_factor=2.0,
> /
> ATOMIC_SPECIES
> Cr 51.9961 Cr.pbe-us_norel_cyrille.UPF
> ATOMIC_POSITIONS crystal
> Cr 0.0000000000 0.0000000000 0.0000000000
> Cr 0.5000000000 0.5000000000 0.5000000000
> K_POINTS automatic
> 8 8 8 1 1 1
>
> All the best,
>
> Ben
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum