[Pw_forum] scan the lattice constant

[Eyvaz Isaev]

Hi again,

I assume total energy calculations are more accurate
using the tetrahedra method rather than MP k-points.
For "smearing" option one has to check also "degauss".

Bests,
Eyvaz.


--- Marco Fornari <fornari at phy.cmich.edu> wrote:

> Hello,
> 
> it may be a problem with the augmented charges of
> the pseudopotential.
> Try to increase ecutrho to explore this
> possibilities.
> Best,
> Marco
> 
> > Dear all,
> > I do a calculation to get the lattice constant of
> Ni crystal.
> > I scan the lattice constant from 6.60 to 6.70 a.u.
> using the bash file
> > below. The experimental value is 6.66 and is
> consistent with my result.
> > But it is clear that the curve departs into two
> parts at 6.66.
> > (see the picture at
> http://www.bsc.ustc.edu.cn/~dxl/download/Graph1.JPG)
> > Would you tell my why and how to solve this
> problem.
> >
> > Thank you!
> >
> > Ding Xunlei
> >
> > for a0 in  6.60 6.61 6.62 6.63 6.64 6.65 6.66 6.67
> 6.68 6.69 6.70
> > do
> > cat >test.in<<!
> > &control
> >     calculation='scf'
> >     restart_mode='from_scratch',
> >     pseudo_dir = '/home/bsc/dxl/pseudo/',
> >     outdir='./'
> >     prefix='zz'
> >     tprnfor = .true.,
> > for a0 in  6.64
> > do
> > cat >test.in<<!
> > &control
> >     calculation='scf'
> > for a0 in  6.65
> > do
> > cat >test.in<<!
> > &control
> >     calculation='scf'
> >     restart_mode='from_scratch',
> >     pseudo_dir = '/home/bsc/dxl/pseudo/',
> >     outdir='./'
> >     prefix='zz'
> >     tprnfor = .true.,
> >     tstress = .true.
> >  /
> >  &system
> >     ibrav=2, celldm(1) =$a0
> >     nat=1,ntyp=1,
> >     nspin = 2,  starting_magnetization(1)=0.7,
> >     ecutwfc = 24.0, ecutrho = 288.0,
> >     occupations='smearing',
> smearing='methfessel-paxton', degauss=0.01
> >  /
> >  &electrons
> >     electron_maxstep= 200
> >     diagonalization=''
> >     conv_thr = 1.0e-8
> >     mixing_beta = 0.2
> >  &cell
> >     cell_dynamics = 'none'
> >     cell_factor = 1.2
> >  /
> >  &ions
> >      ion_dynamics = 'damp'
> >
> >  /
> > ATOMIC_SPECIES
> >  Ni 58.69 Ni.pbe-nd-rrkjus.UPF
> > ATOMIC_POSITIONS
> >  Ni       0.00000000   0.000000000   0.000000000 
> 1 1 1
> > K_POINTS (automatic)
> > 13 13 13 1 1 1
> > !
> >
> >
> >
> >
> >
> > _______________________________________________
> > Pw_forum mailing list
> > Pw_forum at pwscf.org
> > http://www.democritos.it/mailman/listinfo/pw_forum
> 
> 
> 
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