CHARMM Development Project Forums CHARMM Community Bug Reports & Fixes QChem module enabled by default in c41a1?

Hi Charmm

Why is the QChem module being enabled by default in c41a1?
It breaks certain QM/MM options with the DFTB module.

E.g. Do a simple compilation to enable the DFTB module like:

./install.com gnu T gfortran +DFTBMKL

and you cannot use the REMOVE option (Classical energies within QM atoms are removed) in the SCCDFTB group. The offending check is in nbonds/nbonds.src line 316, and should never affect the DFTB module from CHARMM.

It is of course pretty easy to fix by editing install.com and removing qchem from the default option (this in turn messes up the if clauses in mndo97_ltm.src, however, but also trivial to fix).
So there any reason the QChem module is enabled by default as I think it is not at all necessary for most users anyway?

Thanks
Anders Christensen

A number of sites use the Q-Chem interface, so it's likely one of them submitted that change. Have you considered submitting your fixes for code coexistence so that c41a2 might be fixed?

This is part of the effort to allow runtime selection of which QM code to use.

Thanks for the speedy replies! In that case I'd be very hesitant to push any bugfixes, as I don't know the reasoning behind the specific changes (other than runtime selection of QM code.) Any changes I make might just in turn break (or disable) the QChem module.

I put an example that is broken here:
https://dl.dropboxusercontent.com/u/17435887/bugreport.tar.bz2

The examples needs updated filepaths, runs with previous versions of CHARMM, but is broken in c41a1.