As I said before, even if you manage to converge this calculation, you
will not get the binding energy of CaO. If you are lucky, you may get
the energy required to disintegrate the compound, which is really not
the same thing.
Furthermore, putting two atoms in a cell and pulling them far apart is a
guaranteed way to run into DFT shortcomings. The two species may want to
be charged with fractionary charge (ie. Ca^1.5+ and O^1.5-) which do not
exist as isolated ions. Finally, the long range 1/r electrostatic
interaction will never converge.
cheers
On 6/27/20 1:25 PM, Pooja Vyas wrote:
The other way I tried computing isolated energy of Ca and O, is using
the following separate inputs for Ca and O. Are the input scripts valid?
The energies got converged for the following scripts.
On Sat, Jun 27, 2020 at 4:45 PM Pietro Delugas <[email protected]
<mailto:[email protected]>> wrote:
Dear Pooja ____
I might not have understooo what you want to do. ____
__ __
Looking at your input it looks like you are not actually computing
the energy of an isolated system, but instead the energy of ____
rocksalt CaO. In that case it is not isolated system, remove
assume_isolated from the input, use sensible values for alat and the
computation should converge. ____
__ __
Pietro ____
__ __
Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
Windows 10
__ __
*From: *Pooja Vyas <mailto:[email protected]>
*Sent: *Saturday, June 27, 2020 11:56 AM
*To: *Quantum ESPRESSO users Forum
<mailto:[email protected]>
*Subject: *Re: [QE-users] Energy of isolated atom of CaO
__ __
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 <[email protected]
<mailto:[email protected]>> 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 <mailto:[email protected]>
*Sent: *Friday, June 26, 2020 8:12 AM
*To: *Quantum ESPRESSO users Forum
<mailto:[email protected]>
*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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users mailing list [email protected]
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https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________
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