[Wien] Large cell instgen_lapw : word too long

[Laurence Marks]

Many, many points:

1) mpi and k-point parallel are different. For mpi you need software, e.g.
openmpi or the Intel impi and you need to include this in the
configuration. You will need to learn some Linux/computing basics and/or
get help from someone local. It is not really appropriate to ask this list
to help install mpi.

2) Increasing rkmax is not as efficient as mpi in my experience, although
this depends upon the computer architecture (Peter has the opposite
conclusion for small problems).

3) mpi allows you to share the load, for instance have 16 cores working on
the job not one. 16 cores can be ten times faster than one, although note
2) above. For 300 atoms without mpi your problem may not converge before
2018.

4) 1 Re atom in fcc Fe has at least cubic symmetry. If you do not enter
positions right, symmetry/sgroup won't find the symmetry. I would use
cryscon which is cheap, and allows one to generate CIF files with symmetry.
There are other codes.

5) For 300 atoms probably only 1 k-point is needed.

6) Walk before you run. Understand a small model first.

_____
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu


On Nov 6, 2017 3:54 AM, "Chouaib AHMANI FERDI" <ahmaniferdichouaib at gmail.com>
wrote:

Thank you for your feedback.

Mr Gavin Abo,
Unfortunately, I do not have access to supercomputer nor to a cluster. I
will have to stick with my PC for a while. I thought that MPI was for
running jobs on multiple (actual) machines, but since I can run lapw1 in
multiple cores in my Single PC (edit .machine file), I guess I already have
MPI installed.

Mr Peter Blaha,
I realize that 300 atoms is quite a lot including magnetic atoms such as Fe
and RE elements (4f), in fact, 1 cycle took 5 hours to complete, with 40
min for Lapw0, 1h50min for Lapw1 (on 2 cores) for up and down and 16min for
Lapw2 (2 cores) for up and down.
I think the problem is that I am stuck with klist : 2

and if I increase kpoints, so that for example 10 machines would take the
job, (klist 10) I think that Lapw0 will take too long since I cannot run it
in multiple cores.

About the structure, the unit cell without doping consists of 56 atoms with
16 atoms of Fe (fcc lattice) the doping consists of 0.01 RE + 0.01 Re
element doping so that the smallest supercell would be one with 96 Fe
atoms.
I will consider your advice and hope that results from doping smaller
supercell would help explaining the experimental data we obtained.

Faithfully,
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