[Pw_forum] Lattice Parameter too low from experimentally determined. (3.42 ~ 3.52)

[Bramha Pandey]

Dear ELIiot,
Here you are using the pz lda method which always underestimate the lattice
parameter. there is no error in your calculation.



On Tue, Dec 3, 2013 at 5:49 PM, Elliot Menkah <elliotsmenkah at yahoo.com>wrote:

> Hi all,
>
> I'm determining the lattice parameter of Nickel and my convergence test
> is giving me 3.42 Angstroms against and experimentally determined 3.52.
> Previous calculations by other people are showing 3.49 and 3.52
> Angstroms as again.
>
> What could be wrong with my parameters or calculations.
>
> Below is the input file please.
>
>
> #!/bin/sh
> # check whether echo needs the -e option
> #
> executablepath=/home/molecular/espresso-5.0.2/bin/pw.x
> for alat in  6.273 6.369 6.463 6.557 6.652 6.746 6.841 6.935
> do
> #input file
> cat > Ni-$alat.in << EOF
> &CONTROL
>         title = 'Ni-ferro-mag' ,
>         calculation = 'relax' ,
>         restart_mode = 'from_scratch' ,
>         outdir = './temp' ,
>         pseudo_dir = '/home/molecular/Elliot/pseudo' ,
>         prefix = 'Ni-ferromag',
>         tstress = .true. ,
>         tprnfor = .true. ,
> /
>   &SYSTEM
>         ibrav = 2,
>         celldm(1) = $alat,
>         nat = 1,
>         ntyp = 1,
>         ecutwfc = 60,
>         ecutrho = 480,
>         occupations='smearing',
>         smearing='fermi-dirac',
>         degauss=0.003,
>         nbnd=10
>         nspin=2,
>         starting_magnetization(1)=0.5,
> /
>   &ELECTRONS
>          conv_thr = 1.0D-8
>          mixing_beta = 0.2,
> /
>   &IONS
> /
> ATOMIC_SPECIES
>          Ni1 58.6934   Ni.pz-nd-rrkjus.UPF
> ATOMIC_POSITIONS (alat)
>         Ni1       0.000000000   0.000000000   0.000000000
> K_POINTS automatic
>    7 7 7   0 0 0
>
> EOF
> $executablepath < Ni-$alat.in > Ni-$alat.out
> grep "Final energy" Ni-$alat.out >> Ell0.txt
> echo "$alat" >> Lat.txt
> done
> awk '{print $4}' Ell0.txt > Nel.txt
> paste Lat.txt Nel.txt > Final_alat.txt
>
> rm Lat.txt Ell0.txt
>
>
> Thank uou.
>
>
>
> Kind regards,
>
> ELliot.
>
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>



-- 
Thanks and Regards
Bramha Prasad Pandey
GLA University
Mathura (U.P)
INDIA.
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