[Pw_forum] vc-relax cell parameters are not changing
stefano de gironcoli
degironc at sissa.it
Fri Jun 23 10:56:50 CEST 2017
defining A=1 should be the same as defining celldm(1)=1.889...=1/0.529177
stefano
On 23/06/2017 08:30, Isaiah Moses 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 <mailto: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 <mailto: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
> <mailto: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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