[CPMD-list] how to include water in QM part in a QMMM calculation

[Yong Zhang]

Hi CPMDers,

I am setting up a QMMM calculation using cpmd/gromos. I want to include a
small peptide and several water molecules in the QM part. When I first tried
QM=peptide, it is working fine. But when I can added H2O into QM, I got a
error:

###########

 ================================================================
 ==                END OF FORCES INITIALIZATION                ==
 ================================================================

 CPU TIME FOR INITIALIZATION:                      121.27 SECONDS
 MM_DIM| called with: mm_go_mm
 MM_DIM| old status : MM
 MM_DIM| new status : MM
 ***MM_SOLV_CO| SIZE OF THE PROGRAM IS  156032/ 439876 kBYTES ***
  -48.4249572386251       0.274943057696344        6.66473917142948
   1.53747889055130       -3.42658725556664        2.66146148402518
  -16.9038987425283


 PROGRAM STOPS IN SUBROUTINE SHAKE_SM| CONSTRAINT FAILURE
999
##############

The water is part of solute (residue H2O). It is weird because no shake or
constraint is used in either cpmd input or gromos input. Anybody has met the
same problem? Is this related to the SPC water model? How to overcome this
problem? Thanks a lot.

best wishes,

Yong
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