[lammps-users] Class 2 force field - angle, dihedral and improper parameters for restart

Hello,

I am using the class 2 force field for my simulations.
Angles, dihedral and impropers used, require parameters such as
BondBond Coeffs, BondAngle Coeffs etc to be defined.

As per the LAMMPS documentation, these cannot be “set”
using any command, but have to be provided in the read_data file.
However, these values are not stored in the restart file,
and so, I am unable to restart a simulation that uses this forcefield.

My question are:

1> Is there a way of specifying these parameters for a simulation
that starts from a restart file?

2> If not, could you please consider incorporating some method
of specifying these parameters in the input script.
eg. Having bondbond_coeff etc commands?

Any inputs would be appriciated.

Thanks,
Mario

However, these values are not stored in the restart file,
and so, I am unable to restart a simulation that uses this forcefield.

Which quantities do you mean? For example, the bond-bond
and bond-angle coeffs
are written to the restart file with the angle_style class2.

So I think you should be able to restart with all your params.

Steve

Dear Steve,

Thanks for your reply.
I have figured out why the problem was occurring.

Here is what I was doing wrong:

In the input file that reads a restart file,
I was not commenting the line:
angle_style class2

By redefining the angle style, the bondbond and bondangle data was getting lost
and I was getting the error:
All angle coeffs are not set

-even though I was setting the angle_coeffs.

Just for reference, I am attaching two simple test files:
test_step_1.in
test_step_2.in
test.data
potential_params

test_step_1.in (420 Bytes)

test.data (306 KB)

test_step_2.in (332 Bytes)

potential_params (1.14 KB)