[gmx-users] 'fudgeQQ' parameter in the topology file

[Sara Del Galdo]

Dear Gromacs user,

I read from the Gromacs Manual (version 5.1.2) that, while fudgeLJ is used
only when
generate pairs is set to ‘yes’, fudgeQQ is always used.

1. If I set  fudgeQQ = 0.0, will gromacs annulate the 1-4 interactions ?

2. If I explicitly insert a (Coulomb 1-4) scaling factor in my [pairs]
section in the topology file, will Gromacs use both the scaling factor and
fudgeQQ ?
For example, how Gromacs will manage the following case (where the 4-th
coloumn in my pairs section is the scaling factor mentioned above)?

 [ defaults ]
; nbfunc   comb-rule   gen-pairs  fudgeLJ  fudgeQQ
     1       2          no       0.5     0.8333
[ pairs ]
; 1-4 interactions
      1   8   2    0.833   -0.536    0.115    0.2875     0.14940
      1   9   2    0.833   -0.536    0.117    0.2875     0.14940
      1  10   2    0.833   -0.536   -0.033    0.3400     0.22821
      1  23   2    0.833   -0.536   -0.327    0.3105     0.39527
      :  :   :    :        :        :        :          :


Thanks in advance.