[gmx-users] Charge Group Number in itp File (cgnr)

[Andrew DeYoung]

Hi, 

In the [ atoms ] section of an .itp file, there is a column (cgnr) where a
charge group number is given (an integer).  This cgnr column is shown in,
for example, the manual version 4.5.4 in Section 5.7.

My question is, do the charge group numbers have to be _consecutive_
integers?

For some reason, I just noticed after running many simulations that the .itp
file for one of my molecules has a missing charge group number.  For
example, the cgnr column includes the series 425, 426, 428, ... .  That is,
for some very odd reason (I must have made a typo), there is no charge group
with number 427.  Will this cause inaccuracies in the simulation?  I do not
want to rerun all the simulations unless it seems like the missing integer
will cause problems.

Thanks!

Andrew DeYoung
Carnegie Mellon University