Comment 8 for bug 1783785

Dear Nick,

thanks again. I have made some progress. With the new code (version r949)
that you passed to me the compiler worked perfectly. Moreover, now the
spin polarized calculation on the Au_2 dimer does not crash, and produces
the same result as the non-polarized calculation, as expected as the
molecule is not polarized.

However, the spin-orbit calculation still crashes after the SCF cycle
ends. I'm attaching the relevant input and output files to see if you also
reproduce the problem. I noticed weird things, some of them more physical
than computational:
·Before crashing the code prints out the forces. The atomic configuration
  has zero forces at the scalar relativistic level, and S-O effect should
  be a small correction. However, the forces at that atomic configuration
are huge, bigger than 100 eV Ang. It makes not much sense.
·It seems that the orbitals are not evenly distributed between the four
nodes. I'm not sure if this is an error or it is the intended way?

I know that S-O is still under development and it may be normal to have
some errors. I also read in the manual that the S-O flag does not work yet
with optimizations. Maybe this implies that the forces can be non sense?

Thanks in advance for any help.

Andres Aguado

On Sun, 29 Jul 2018, Nick Papior wrote:

> Perhaps it is not difficult to fix. Could you try this:
> https://bazaar.launchpad.net/~siesta-maint/siesta/rel-4.1/tarball/949?start_revid=949
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1783785
>
> Title:
> spin-polarized and spin-orbit calculations on a gold dimer crash
>
> Status in Siesta:
> New
>
> Bug description:
> Hi,
>
> I am using siesta-4.1-b3 version. I am calculating the gold dimer as a
> simple test of my pseudo and basis set. I have done all the main tests
> using a non-polarized calculation as Au_2 is obviously non-polarized.
> I found no problems at all. Then I wanted to see the effect of S-O
> coupling, but I first tried a spin-polarized calculation just as a
> sanity test. Both calculations (either spin-polarized or spin-orbit)
> proceed apparently well and the SCF convergence is reached. Just after
> that, when I guess the code prints out the final information (energy
> decomposition, dipole moment, etc) the code crashes, both in parallel
> and in serial (in serial I can read "Bus error"; in parallel not much
> information).
>
> I attach both the psf file with the pseudo and the fdf file below. I
> have checked that the mistake is only in the "Spin" order. If you set
> "Spin non-polarized" it works. If you just change this to "Spin
> polarized" it crashes.
>
> Any help will be appreciated. I'm not sure of this is a bug of a
> compiling problem, but the code compiled without any problem. And the
> spin-unpolarized calculation gives almost exactly the same result as
> 4.0.2 version, so it seems OK.
>
> Thanks in advance
>
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