[gmx-users] Carbon Nanotube Force Field

[Bob Johnson]

Hello,
I'm simulating a system involving carbon nanotubes. As an initial test of my
force field I want to simulate a single infinite carbon nanotube. I've done
simulations at constant volume and constant pressure. I've also run some energy
minimizations. However, it seems that the energy is always too high and the tube
wants to develop kinks and collapse on itself. I'm using the following force
field obtained from the following paper: Guo, Karasawa, Goddard, Nature, Vol.
351, 1991

Bonds:
Morse potential (function 3 in GROMACS)
D = 478.9 kJ/mol
b_0 = 0.1418 nm
beta = 21.867 nm^-1

Angles:
G96 angle (function 2 in GROMACS)
theta_0 = 120.00
fc = 562.2 kJ/mol

Dihedrals:
Proper dihedral (function 1 in GROMACS)
theta_max = 180.00
fc = 12.06 kJ/mol
mult = 2

Pairs:
L-J (function 1 in GROMACS)
c6 = 4*eps*sig^6 = 5.7353e-3 kJ nm^6/mol
c12 = 4*eps*sig^12 = 1.8707e-5 kJ nm^12/mol

Can anyone verify that this is correct? Any suggestions on stabilizing the
nanotube?
Thanks,
Bob