[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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