[Pw_forum] vc-relax cell parameters are not changing

[Isaiah Moses]

Hi Paolo,
But how does one set CELL_PARAMETERS (angstrom)?
Because I observe that the output I obtain from vc-relax is automatically
set to
CELL_PARAMETERS (alat=  8.11400000).
Does that has to do with the unit of celldm?

I must be missing something on theses units' usage.

I appreciate your usual prompt response,
Isaiah

On Fri, Jun 23, 2017 at 7:16 AM, Paolo Giannozzi <p.giannozzi at gmail.com>
wrote:

> And, by the way, it is a bad habit to set the lattice parameter to the
> conversion factor between a.u. and A. One should use instead
> CELL_PARAMETERS (angstrom)
> to specify lattice vectors in A
>
> Paolo
>
> On Fri, Jun 23, 2017 at 4:55 AM, Stefano de Gironcoli <degironc at sissa.it>
> wrote:
> > The lattice parameter does not change, it is not updated along vc-relax,
> the
> > lattice vectors do.
> > Using bfgs you don't need to define dt
> >
> > stefano
> > (sent from my phone)
> >
> > On 23 Jun 2017, at 01:55, Brendan Smith <mrbsmith58 at gmail.com> wrote:
> >
> > Hello all,
> >
> > I am doing a the following vc-relax calculation and the unit cell
> paramters
> > are not changing. I have looked at other posts which descirbes similar
> > problems, but it does not remedy my problem. Below is my input.
> > Best,
> > Brendan
> >
> >
> > &CONTROL
> >   calculation = 'vc-relax',
> >   dt = 20.67055,
> >   nstep = 1000,
> >   pseudo_dir = './'
> >   outdir = './',
> >   prefix = 'x',
> >   disk_io = 'low',
> > /
> >
> > &SYSTEM
> >   ibrav = 0,
> >   celldm(1) = 1.89,
> >   nat = 16,
> >   ntyp = 3,
> >   nspin = 1,
> >   nbnd = 120,
> >   ecutwfc = 70,
> >   ecutrho = 560,
> >   tot_charge = 0.0,
> >   occupations = 'smearing',
> >   smearing = 'gaussian',
> >   degauss = 0.005,
> >   nosym = .true.,
> > /
> >
> > &ELECTRONS
> >   electron_maxstep = 1000,
> >   conv_thr = 1.D-5,
> >   mixing_beta = 0.45,
> > /
> >
> > &IONS
> >   ion_dynamics = 'bfgs',
> >   ion_temperature = 'andersen',
> >   tempw = 300.00 ,
> >   nraise = 1,
> > /
> >
> > &CELL
> >   cell_dynamics = 'bfgs',
> >   press_conv_thr = 0.5,
> >   cell_factor = 2.0,
> >   cell_dofree = 'all',
> > /
> >
> > ATOMIC_SPECIES
> >  O  15.9994  O_pbe_v1.2.uspp.F.UPF
> >  V  50.9415  V_pbe_v1.uspp.F.UPF
> >  Pb 207.2    Pb.pbe-dn-rrkjus_psl.0.2.2.UPF
> >
> > K_POINTS automatic
> >  3 3 3 0 0 0
> >
> > CELL_PARAMETERS (alat)
> >        11.5439996719         0.0000000000         0.0000000000
> >         0.0000000000         3.5710000992         0.0000000000
> >         0.0000000000         0.0000000000         4.3829998970
> >
> > ATOMIC_POSITIONS (alat)
> >  V    6.940599    0.892750    0.475994
> >  V    4.603400    2.678250    3.907006
> >  V   10.375401    0.892750    0.475994
> >  V    1.168599    2.678250    3.907006
> >  O    4.974309    0.892750    4.370728
> >  O    6.569691    2.678250    0.012272
> >  O    0.797690    0.892750    4.370728
> >  O   10.746309    2.678250    0.012272
> >  O    6.978348    0.892750    2.058695
> >  O    4.565652    2.678250    2.324305
> >  O   10.337652    0.892750    2.058695
> >  O    1.206349    2.678250    2.324305
> >  O    8.658000    0.892750    0.003506
> >  O    2.886000    2.678250    4.379493
> >  Pb   8.500000    2.500000    1.500000
> >  Pb   3.000000    1.500000    3.000000
> >
> >
> >
> >
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>
>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
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>



-- 
Isaiah Abu Moses
Graduate Student,
Physics Department,
University of Ibadan,
Nigeria
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