[Pw_forum] vc-relax cell parameters are not changing

[Paolo Giannozzi]

I don't remember what the code prints during a vc-relax calculation,
but I know for sure that the output of ATOMIC_POSITIONS and
CELL_PARAMETERS is in a format that can be used as input.

On Fri, Jun 23, 2017 at 8:30 AM, Isaiah Moses <imoses87 at gmail.com> wrote:
> 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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-- 
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