Dear all,

I have questions about commands of GULP:

- I want to use the fifth-order Ryckaert-Bellemans torsion potential. What are the meanings of ‘<flags
*norder+1>’ and 'norder*coefficients’ in the help file? Can you give me an example how to express the fifth-order Ryckaert-Bellemans potential? - I found some examples. What are the meanings of kcal in the command ‘lennard 12 6 zero kcal epsilon combine product all’ and ‘harmonic intra bond single kcal’?
- How can I set the coulombic 1-4 scale factor? I used the command ‘coulomb_subtract x13 0.5’, but when I output lammps file, I found the coulombic 1-4 scale factor in special_bonds is 0. And I used the command’lennard epsilon geometric 12 6 x13 all 0.5

10.0’, and the lj 1-4 scale factor in lammps file is 0.5, which is normal.

Best Regards,

Wang Qiang.