[gmx-users] dihedraltype parameters

[akari karin]

hi, I am simulating carbon nanotubes in gromacs. I am preparing my
forcefield.itp file and i want to use the twofold cosine torsion as my
dihedraltype. The form of the potential i want use is -

0.5 * K_cphi*(1- cos(2*phi_ijkl))

I have 2 questions regarding this.

1. I saw the chapter 4 in the manual and i was wondering if i should use
Ryckaert-Bellemans function(with F1=F3=F4=F5= 0 and F2=K_cphi) or not.

2. If i use  Ryckaert-Bellemans function, should i use func. type of 3 and

C0= K_cphi
C1=0
C2=-K_cphi
C3=0
C4=0
C5=0 ?


Thanks in advance.