[lammps-users] About how to add force and atom type


I’d like to have several questions as follows:

1.I want to study the mechanical properties��specially, the bending and tension behavior�� of metal nanorod/nanowire by molecular dynamics. Is LAMMPS able to simulate the bending and tension behavior of nanorod? If LAMMPS can, how should the right concentrated force be added? How about the tension case? I have studied the crack and shear examples of the LAMMPS distribution. In those cases, the crack and shear behavoirs are simulated by adding velocity in all the atoms of different group. But for bending cases, I wonder whether that is suitable.

2.The number of atom types set in the data file is greater than the number of the elements. And not all the atom types are used or set in the Atoms section. How should the pair coefficients be set by the pair_coeff command in this case taking into consideration the fact that all pair coefficients must be set in the data file or by the pair_coeff command before running a simulation? I want to have a better display in the postprocessing. Can you explain HOW TO by an example of SiC or others? eg,pair_coeff * * SiC.tersoff C Si ? ? ? ? ?

Any suggestion will be appreciated!


Regards all


For your 1st Q, you'd have to describe what kind of boundary condition
you want to apply. Various LAMMPS fixes can be applied to a set of
atoms to move them as you wish.

For your 2nd Q, if you don't have any atoms of a certain type, then
it doesn't matter what you set the pair coeffs to, so long as you set them.
So set all the fictitious types to C or Si if you want for Tersoff.