[gmx-users] Can't do GB electrostatics; the implicit_genborn_params section of the forcefield is missing parameters for

[xi zhao]

Dear gmx-users:
When I try to simulation a system: protein + ligand molecule using the Implicit Solvent method. the parameters of Ligand were produced by acpype, but when grompped, the appeared" 
" Velocities were taken from a Maxwell distribution at 300 K
GB parameter(s) missing or negative for atom type 'o'
GB parameter(s) missing or negative for atom type 'os'
GB parameter(s) missing or negative for atom type 'c'
GB parameter(s) missing or negative for atom type 'c3'
GB parameter(s) missing or negative for atom type 'hc'
GB parameter(s) missing or negative for atom type 'h1'
-------------------------------------------------------
Program grompp_d, VERSION 4.5.3
Source code file: grompp.c, line: 1123
Fatal error:
Can't do GB electrostatics; the implicit_genborn_params section of the forcefield is missing parameters for 6 atomtypes or they might be negative."
when I modified "amber99sbr.ff/gbsa.itp by adding the atomtype of ligand, the problem is still the same, 
please give me some suggestions
Thank you! 
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