CCL:G: Quantum chemistry interoperability library?

This was at least part of the point of the QC JSON schema.
 MolSSI sponsored at least one workshop where this was discussed and a draft was
 At that workshop several years ago, in which many developers, including quantum
 programs (NWChem, Q-Chem, Psi4, Molpro, GAMESS .. I know pretty much the entire
 community was invited), analysis programs (Horton), community programs (cclib,
 Open Babel, Avogadro, Jmol, etc.) were there. It was a big enough meeting that
 I'm sure I missed some people.
 Issues of normalization, metadata, input files (e.g. keywords), program-specific
 features, etc were all discussed.
 The idea was to first get out a "better Molden" interchange.
 So if you (personally) and/or MolSSI want to push this again, it would be great.
 Perhaps either a virtual meeting or discussion forum can get things moving
 P.S. The work and some discussion is here:
 Prof. Geoffrey Hutchison
 Department of Chemistry
 University of Pittsburgh
 tel: (412) 648-0492
 email: geoffh[*]
 twitter: [*]ghutchis
 > On Dec 29, 2021, at 8:01 PM, Susi Lehtola susi.lehtola[A]
 <owner-chemistry[*]> wrote:
 > Sent to CCL by: Susi Lehtola [susi.lehtola{=}]
 > Hello,
 > I am again hitting my head against the wall, since I am having trouble
 > passing data from one quantum chemistry code to another.
 > What we are missing as a community is a standard interoperability
 > library for passing basis set and wave function data from one program to
 > another. The de facto standard is GAUSSIAN's formatted checkpoint
 > library, but it also has some deficiencies; for instance, it's not
 > machine precision.
 > Because the library should store all the necessary data for at least SCF
 > wave functions, that is, the Gaussian basis set and the molecular
 > orbitals (MOs) and their occupation numbers, an interface to this
 > library could also serve as a tool for checkpointing calculations that
 > have not converged.
 > Some pieces of the necessary functionality are certainly around. Many
 > quantum chemistry programs have implemented their own formatted
 > checkpoint i/o functions. Quantum chemistry analysis programs have
 > needed to implement their own parsers for the .fchk / MOLDEN / etc formats.
 > I do not think that writing such a common interface library should be
 > too difficult. All that is needed is
 > 1. a data structure that is able to express the data in a common format and
 > 2. input and output functions to translate the data from/to specific
 > quantum chemistry code formats.
 > In addition to the .fchk and molden formats, the common interface
 > library should also be able to read various programs' native data files
 >> from disk, like DENS and XDENS in TURBOMOLE.
 > Since many pieces of the puzzle are already around, and the problem
 > affects the whole community, I would like to get everyone's feedback on
 > this idea.
 > If there was, say, a portable open-source C++ library with C, Fortran
 > and Python frontends for handling molecular wave function data, would
 > you be willing to use it in your own program package? What kinds of
 > features would you need in it? Does such a library already exist?
 > Susi
 > PS. I work as a Software Scientist at the Molecular Sciences Software
 > Institute at Virginia Tech (, but I am sending this
 > message from my Helsinki address since it's what I've used here for
 > close to a decade.
 > --
 > ------------------------------------------------------------------
 > Mr. Susi Lehtola, PhD             Adjunct Professor
 >   University of Helsinki
 >     Finland
 > ------------------------------------------------------------------
 > Susi Lehtola, FT                  dosentti
 >   Helsingin yliopisto
 > ------------------------------------------------------------------
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