[lammps-users] RCFF


I am trying to model interactions between Carbon & silicon atoms using RCFF or COMPASS. I have the parameters for these force fields. But i don;t know how to include them in lammps. I mean the format & also the order of parameters. Also, i want to know if we can control the no of bonds between C & Silicon using these force fields.

I want a part of my system to have a sinusoidal motion at a particular freq. SO, i am using fix move/wiggle for that. But i am getting an error. I am attaching part of my code.Please take a look & please let me know the error.

region 5 block INF INF INF INF 38.0 38.5 units box
group point region 5

region 6 block INF INF INF INF -41.0 38.0 units box
group body region 6

fix 3 all nvt 35.0 35.0 0.2 drag 5.0

timestep 0.001

thermo 10
run 200000

unfix 3

fix 4 body nve
fix 5 point move wiggle 0.0 6.0 0.0 12.0
timestep 0.001
run 1000000
unfix 5
unfix 4

The COMPASS ff in LAMMPS is all the pair, bond, angle, etc styles
that have a class2 in them. Other than reading the doc pages, inputting
the correct coeffs for each style, and trying it out, I don't know
what to tell you.

What is the error you are getting with fix move/wiggle, and have you visualized
the system?