Energy increasing and crashing in QMMM

[Dries Van Rompaey]

Hi everyone,

I'm seeing extreme increases in energy during SCF in my QMMM system. It's a 
protein:ligand complex which I have previously simulated using 
semi-empirical QMMM (with PM6), but I am having difficulties moving it to 
DFT. Problems occur both using wavelet and MT as poisson-solver.
Using MT, the SCF optimisation prints out:

> 1 OT CG       0.15E+00    4.3     0.07338929      -245.3521031334 -2.45E+02
> 2 OT LS       0.16E-01    2.1                     -105.1518004766
> 3 OT CG       0.16E-01    3.9     0.08689260      -214.7379955081  3.06E+01
> 4 OT LS       0.16E-03    2.0                   589356.6222967544
> 5 OT CG       0.16E-03    3.8     1.58848424     34863.9952881550  3.51E+04
> 6 OT LS       0.16E-05    2.0                474895064.4618470073
> 7 OT CG       0.16E-05    3.9    87.13775893  45190083.4925281629  4.52E+07
> 8 OT LS       0.16E-07    2.0                ********************
> 9 OT CG       0.16E-07    3.8  9824.70615457 ********************  4.98E+10


Using wavelet:

> 1 OT CG       0.15E+00    6.3     0.13953650      -490.9063955586 -4.91E+02
> *** WARNING in pw/ps_wavelet_methods.F:236 :: Density non-zero on the ***
> *** edges of the unit cell: wrong results in WAVELET solver           ***
> 2 OT LS       0.30E+00    3.3                ********************
> *** WARNING in pw/ps_wavelet_methods.F:236 :: Density non-zero on the ***
> *** edges of the unit cell: wrong results in WAVELET solver           ***
> 3 OT CG       0.30E+00   10.0     1.1529+103 ********************  1.51+106


I have tried to increase the size of the QM box, but my box is now at 
45x45x45 Å and my molecule is no longer than 17 Å. As far as I can tell 
from the posts on the mailing list, this box size should be sufficient to 
contain the system.  All files can be found on the dropbox link 
here: https://www.dropbox.com/sh/33lm80977zedcua/AADsNbFIpm_hmyvS1N_xF5DBa?dl=0


Thanks for your time,
Kind regards,

Dries

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