[gmx-users] conversion of the AMBER parameters to GROMACS with negative barrier height values

[ABEL Stephane 175950]

Hello all, 

I am trying to convert some GLYCAM parameters to do simulations with the GROMACS code. In the glycam force field, several dihedral terms have negative barrier height values, for instance, -20 in the following parameter:  

 Os-Cj-Cj-Ha   1  -20.00          0.0             2          SCEE=1.0 SCNB=1.0 copy of Os-Ck-Ck-Ha

So I wonder if  It is safe to use a negative value in case of GROMACS  for the amplitude 

;i   j	 k   l	     func  phi0	   cp	       mult
 Os-Cj-Cj-Ha   9     0.0     -83.680    2

Sorry if it is a stupid question and thanks in advance for your response

Stephane