From: John Stone (
Date: Wed Apr 10 2019 - 15:54:50 CDT

  I didn't write the Molden plugin, but a quick read through the code
indicates that it's determining the number of geometries/frames/timesteps
to read from a particular Molden file section, and that it is NOT trying
to read them in the form of concatenated output files. Apparently a single
Molden output can contain multiple geometries/timesteps, so that's how
the plugin was structured. It might be possible to teach VMD to allow
you to use "mol addfile" to append a compatible QM config/run to an
existing molecule in VMD, but a lot of work would have to go into checking
that they use the same basis set and all of that, essentially all of the
information that would normally be redundant among multiple output files
that arise from the same input parameters.

The Molden plugin was written long before the NAMD QM/MM feature
(Molden orbital parsing was added 10 years ago), so this wasn't previously
a consideration. We've been trying to get a Terachem license going
here to be able to develop new support for it in the NAMD QM/MM feature,
but that has been stalled waiting on the Stanford team for a technical
issue with avoiding unnecessary Terachem restarts, as I understand it.

In the mean time, you might read more of the Molden format and the
moldenplugin source code, and you could probably modify it to
allow the concatenation scheme you're using, or something like it.
Until our QM/MM team have access to Terachem, there's probably
not much we can do to help out with this particular issue in the short-term.

Best regards,
  John Stone

On Wed, Apr 10, 2019 at 08:15:17PM +0000, McGuire, Kelly wrote:
> Anyone have any experience or ideas on how to read in .molden files that
> have been concatenated during a QMMM, just as we can do with ORCA .out
> files? I have concatenated my qmmm.molden files for each step, but when I
> load it as a MOLDEN filetype, it just reads in the first output in the
> concatenated file and ignores all of the other outputs. So far, using
> Terachem instead of ORCA for my QMMM, I have ~4000 steps. I would like to
> see the orbitals for each step just like with ORCA.
> Kelly L. McGuire
> PhD Candidate
> Biophysics
> Department of Physiology and Developmental Biology
> Brigham Young University
> LSB 3050
> Provo, UT 84602

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