[gmx-users] Fwd: QMMM calculation

[Christian Burisch]

Pradip Kumar Biswas wrote:

Hi,

>> calculation. I have seen you using OPLS for your calculation. Is it
>> possible to use Gromos force field, where polar hydrogen is used.

> You should be able to use any force field implemented or supported by 
> Gromacs. QM/MM does not depend upon the force field.

> I could not really get what you mean. 

since I am interested in this topic, too, but without having used your 
interface yet: I guess the question is where do the nonpolar hydrogens 
(which usually are missing in GROMOS united atoms ff, so you cannot 
put them in the [QM] index group) come from when switching from MM to 
QM? Are they added e.g. from geometric criteria by your interface or 
CPMD (I guess not), are they just ignored (definitely not) or do one 
has to generate an all-atom QM part of the system in the first place 
(i.e. coordinates and topology; I guess this is the case)? That would 
mean a mixture of united- and all-atom ff.

Regards

Christian