[QE-users] Energy of isolated atom of CaO

[Pooja Vyas]

I tried the way you suggested, tried replacing "relax" by "scf", however ,
I still face the same issue: No convergence even after 100 iterations.
Following is the input file:

PS: I want to calculate isolated energy of CaO using example05/PW (i.e
Martyna-Tuckerman) method.
#!/bin/sh

for a in 30
do

cat > ${a}.in << EOF
&CONTROL
  calculation  = 'relax'
  prefix       = "${a}",
  pseudo_dir   = "/home/userpooja/pv/cohesive/pseudo/",
  outdir       = "/home/userpooja/pv/cohesive/",
/
&SYSTEM
  ibrav     = 1,
  celldm(1) = $a,
  nat       = 2,
  ntyp      = 2,
  ecutwfc   = 100.D0,
  nbnd      = 8
  assume_isolated = 'martyna-tuckerman'
/
&ELECTRONS
  conv_thr    = 1.D-8,
  mixing_beta = 0.7D0,
  startingwfc = 'random'
/
&IONS
/
ATOMIC_SPECIES
Ca  40.078  Ca.pbe-nsp-van.UPF
O  15.999  O.pbe-van_ak.UPF
ATOMIC_POSITIONS
Ca 0.0 0.0 0.0
O  0.5 0.5 0.5
K_POINTS Gamma

EOF

mpirun -np 40 -machinefile x1 /apps/codes/qe/6.4/bin/pw.x < ${a}.in >
${a}.out
done

Any kind of help is appreciated.
Thanks and Regards.

On Fri, Jun 26, 2020 at 11:58 AM Pietro Delugas <pdelugas at sissa.it> wrote:

> Hello
>
>
>
> In ATOMIC_POSITIONS  you need to specify the units that you are  using for
> the coordinates, if you don’t put anything he program assumes alat units
> and puts the 2 atoms very far apart.
>
>
>
> If you actually wanted  compute the two separated atoms specifying
> startingwfc=’random’ in the &electrons name list may help.  In this case I
> would also chose calculation=’scf’ in &control.
>
>
>
> Regards - Pietro
>
>
>
> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows 10
>
>
>
> *From: *Pooja Vyas <poojavyas595 at gmail.com>
> *Sent: *Friday, June 26, 2020 8:12 AM
> *To: *Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
> *Subject: *[QE-users] Energy of isolated atom of CaO
>
>
>
> Dear users,
>
> I want to calculate cohesive energy of CaO. I'm using cluster_example/PW
> which uses assume_isolated = 'martyna_tuckerman' . Following is my input
> script:
>
>
>
> #!/bin/sh
> for a in 30
> do
> cat > ${a}.in << EOF
> &CONTROL
>   calculation  = 'relax'
>   prefix       = "${a}",
>   pseudo_dir   = "/home/user/pv/cohesive/pseudo/",
>   outdir       = "/home/user/pv/cohesive/",
> /
> &SYSTEM
>   ibrav     = 1,
>   celldm(1) = $a,
>   nat       = 2,
>   ntyp      = 2,
>   ecutwfc   = 100.D0,
>   assume_isolated = 'martyna-tuckerman'
> /
> &ELECTRONS
>   conv_thr    = 1.D-8,
>   mixing_beta = 0.7D0,
> /
> &IONS
> /
> ATOMIC_SPECIES
> Ca  40.078  Ca.pbe-nsp-van.UPF
> O  15.999  O.pbe-van_ak.UPF
> ATOMIC_POSITIONS
> Ca 0.0 0.0 0.0
> O  0.5 0.5 0.5
> K_POINTS Gamma
>
> EOF
>
> mpirun -np 40 -machinefile x1 /apps/codes/qe/6.4/bin/pw.x < ${a}.in >
> ${a}.out
> done
> done
>
>
>
> My lattice constant is around 8 a.u , so I assumed the box size to be 3
> times of it. But when I run the script, the convergence was not achieved
> even after 100 iterations. Then I tried to take small box size of about 16
> bohr. That too didn't work. Then I even tried reducing ecutwfc and
> mixing_beta..but same error was obtained. Can anyone suggest what can I do
> to resolve the issue?
>
> Any kind of help is appreciated.
>
> Thanks and regards.
>
>
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