[Pw_forum] very high pressure in scf

[Sanjeev Gupta]

Dear Sir,
Thanks for reply.


On Thu, May 26, 2011 at 10:23 PM, Stefano de Gironcoli <degironc at sissa.it>wrote:

>  with this input the Fe-N distance is some 1.2 A... I'm pretty sure it
> cannot be the intended structure
> Are you sure the system is not in crystal coordinate ?
>  stefano
>
Yes, its true that  while looking from xcrysden particularly the bond
lengths between the Fe-N and N-N  but i am very surprised why both ABINIT
and PWSCF code gives such vast Difference in calculated Pressure for the
identical geometry which is not cleared yet. Here the bond lenth Fe-N is
~1.24Ang.
Please Suggest More.



>

>

> On 05/26/2011 04:13 PM, Sanjeev Gupta wrote:
>
> Dear Maxim
>
> Thank for kind reply.
>
> My unit cell is as same in ABINIT  as in pwscf in Bohr  unit. In addition I
> am using the spacegroup 166   (R3(bar)M) space group with conventional unit
> cell rather than primitive unit cell the lattice parameter is taken as below
> 1. for abinit
>
> a=5.359168252 Bohr
> b=5.359168252 Bohr
> c=20.08294707 Bohr
>
> 2. for PWSCF
>
> ibrav=4,
> celldm(1) = 5.359168242 Bohr
> celldm(3) = 3.7474
>
> Part of my input file is :
>
> PWSCF
>
> &control
>     calculation = 'scf'
>     prefix='FeN2',
>     restart_mode='from_scratch',
>     outdir='./'
>     pseudo_dir = '/',
>     tstress = .true.
>     tprnfor = .true.
>     etot_conv_thr = 1.0d-5,
>     forc_conv_thr = 1.0d-4,
>  /
>  &system
>     ibrav=4,
>     celldm(1) = 5.359168242,
>     celldm(3) = 3.7474
>     nat=9,
>     ntyp=2,
>     nosym =.true.,
>     ecutwfc = 20,
>     ecutrho=200,
>     occupations='smearing',
>     smearing='m-p',
>     degauss=0.001,
>  /
>  &electrons
>      mixing_mode     = "local-TF",
>      mixing_beta     =  0.700000,
>      conv_thr        =  1.0d-10,
> /
> ATOMIC_SPECIES
> Fe  55.845  Fe.pbe-sp-van.UPF
> N   14.0067 N.pbe-van_ak.UPF
> ATOMIC_POSITIONS
> Fe    -1.8503717077E-17 -1.8503717077E-17 -1.8503717077E-17
> N     -1.8503717077E-17 -1.8503717077E-17  4.4000000000E-01
>
> ..........................................
>
> N      3.3333333333E-01  6.6666666667E-01  2.2666666667E-01
> K_POINTS automatic
> 6 6 6 0 0 0
>
>
> Best Regards
>
>
> Sanjay D. Gupta
> Research Fellow
> Department of Physics,
> Bhavnagar University, Bhavnagar-364 022
> Gujarat, Mobile-9879666643email:guptasanjay_56 at yahoo.co.in
>
>
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