[gmx-users] topol. top file

[Dhrubajyoti Maji]

Dear gromacs users,
                 I am writing the top file for liquid acetamide system for
OPLS FF. I am confused with the [pairs] section. Should I give the 1-4
atom numbers here or left it empty for OPLS to calculate this by itself ?
Another question is, in [ atomtypes] section what should be written first ,
sigma or epsilon ?
Thanks and regards
Dhrubajyoti Maji