Hello everyone.
I am LAMMPS beginner and try strain simulation in carbon nanotube.
I am aiming to compress the carbon nanotube in the axis direction and obtain the Young’s modulus.
I did this simulation on airebo, and got good result.
However, I did the same simulation on class2 and I could not get good results.
Specifically, it shows much higher pressure than the airebo result.
The input file is shown below, strain simulation was done after relaxation simulation.
The data file was created using the nanotube builder of VMD and added bond (and angle, so on) for periodic boundary.
Please tell me how to solve this probrem.
----------------relaxation---------------
units metal
boundary f f p
atom_style full
pair_style lj/class2 3
bond_style class2
angle_style class2
dihedral_style class2
improper_style class2
mass 1 12.0
pair_coeff * * 0.068 3.915
bond_coeff * 1.4170 470.8361 -627.6179 1327.6345
angle_coeff * 118.9000 61.0226 -34.9931 0.0000
angle_coeff * bb 68.2856 1.4170 1.4170
angle_coeff * ba 28.8708 28.8708 1.4170 1.4170
dihedral_coeff * 8.3667 0.0000 1.2000 0.0000 0.0000 0.0000
dihedral_coeff * mbt 27.5989 -2.3120 0.0000 1.4170
dihedral_coeff * ebt -0.1185 6.3204 0.0000 -0.1185 6.3204 0.0000 1.4170 1.4170
dihedral_coeff * at 1.9767 1.0239 0.0000 1.9767 1.0239 0.0000 118.9000 118.9000
dihedral_coeff * aat 0.0000 118.9000 118.9000
dihedral_coeff * bb13 53 1.4170 1.4170
improper_coeff * 7.1794 0.0000
improper_coeff * aa 0.0000 0.0000 0.0000 118.9000 118.9000 118.9000
velocity all create 1.0 780042
fix 1 all nve
fix 2 all temp/rescale 1 1.0 1.0 0.05 1.0
fix 3 all press/berendsen z 0.0 0.0 500.0
----------------stress---------------
units metal
boundary f f p
atom_style full
pair_style lj/class2 3
bond_style class2
angle_style class2
dihedral_style class2
improper_style class2
fix 1 all nve
fix 2 all temp/rescale 1 1.0 1.0 0.05 1.0
fix 3 all deform 1 z trate -0.001