QM-MM QChem calculation stops without error

Questions
#1

Hi,

we are trying to run qm-mm calculation using qchem for system with molecular probe inside active site of protein in water using default qchem CHARMM27 force field. Molecule (first 90 atoms in input) should be treated at QM level and environment at MM level. But there is a problem with this calculation, that it stops at the beginning without any error message.

So, the output looks like this:
**** Step 1: MM force contributions ****
CHARMM27 force field loaded.
Determining angles, torsions, etc. from user defined input
Determining VDW/Coulomb pairs… (useList = 0)

Time req’d to get MM system information: 0.3 s (CPU) 0.7 s (wall)

The input is here: QMM input - JustPaste.it

Please look at it.
When we tried to do the same but with only molecule (first 90 atoms in input) and 3 water molecule, it was working, but it’s not working for full system.

There is also XYZ file, if you would like to see this system in VMD or something.

Thanks you in advance!

Łukasz Milewski
l.milewski@cent.uw.edu.pl

#2

Hello Łukasz,

Can you post the snippet of the output or send the output file to support@q-chem.com? I suspect that the linked MM atoms not being carbon cause the error. You may have to increase/decrease the QM region so the linked MM atoms are always carbon.

#3

Hi,

thank you for the answer!

You can view output here:

https://justpaste.it/8ov6z

#4

Hello Łukasz,

Thank you for providing the output file. It seems that the CHARMM27 does not contain information for electrostatics interactions of some atom types. You may consider user-defined force field (11.3.3 Using the Stand-Alone QM/MM Features‣ 11.3 Stand-Alone QM/MM Calculations ‣ Chapter 11 Molecules in Complex Environments: Solvent Models, QM/MM and QM/EFP Features, Density Embedding ‣ Q-Chem 5.4 User’s Manual) while we are fixing the segfault issue. I will keep you updated