[Pw_forum] Noncolin vs Nspin=1 for Chromium

[Ben Palmer]

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