search

selimsami / qforce

Apache License 2.0
57 stars 13 forks source link

The default n_excl #8

Closed xiki-tempula closed 2 years ago

xiki-tempula commented 2 years ago

In https://qforce.readthedocs.io/en/latest/options.html, it is said that 

n_excl, int
 default: 2, from Choices(2, 3)
Number of first n neighbors to exclude in the forcefield

I wonder if this means that the default n_excl is 2? Instead of the commonly used 3?

selimsami commented 2 years ago

It does mean that. But I would say that commonly n_excl=2 is used. The 3rd neighbors are the 1-4 interactions, which are commonly not excluded but have special pair interactions. Q-Force follows the same approach as the parent transferable FF.

xiki-tempula commented 2 years ago

I see what you mean now. Sorry that I didn't read the description. In Gromacs topology file, nrexcl is usually set to 3 so I thought that they are the same.

selimsami commented 2 years ago

Yeah I see why it is confusing, maybe worth renaming the variable. The GROMACS topology file will have nrexcl=3 with both n_excl 2 and 3, but in the former case, it will have the pair interactions turned on.