Dear Lammps Developers,
I am simulating a rigid sphere(Diamond) scratching a substrate(Si).
the rigidity is defined by:
fix 3 nanoparticle rigid/nvt single temp 300.0 300.0 0.1 force 1 off off on torque 1 off off off
In “z” direction a constant force applied on the rigid sphere implemented by:
fix 9 nanoparticle addforce 0.0 0.0 ${forceup}
and in “x” direction a constant velocity applied on it implemented by:
fix 11 nanoparticle move linear $V NULL NULL units box
The problem is during the movement sphere particle deformed to a ellipsoid.
Would you help me fix the problem.
following is Simplified script:
########## Initialization #########
units metal
dimension 3
boundary p p s
atom_style atomic
######### create geometry ###########
…
…
############### Interatomic potential ##################
pair_style hybrid tersoff morse 2.5
pair_coeff * * tersoff SiC.tersoff Si Si Si C
pair_coeff 1*3 4 morse 0.435 4.6487 1.9475
Dear Lammps Developers,
I am simulating a rigid sphere(Diamond) scratching a substrate(Si).
the rigidity is defined by:
*fix 3 nanoparticle rigid/nvt single temp 300.0 300.0 0.1 force 1 off off
on torque 1 off off off *
In "z" direction a constant force applied on the rigid sphere implemented
by:
*fix 9 nanoparticle addforce 0.0 0.0 ${forceup}*
and in "x" direction a constant velocity applied on it implemented by:
*fix 11 nanoparticle move linear $V NULL NULL units box*
The problem is during the movement sphere particle *deformed to
a ellipsoid.*
Would you help me fix the problem.
this seems more like a bad choice of integrators to me. LAMMPS should have
warned you about it.
i don't really see the need, you can easily establish a constant velocity
motion by using the velocity command with the add option and the set the
velocity for the y direction to 0.0. then use fix setforce 0.0 0.0 NULL to
wipe out forces in x and y. voila, no more need to use fix move and
conflicting position and velocity updates from two competing integrator
fixes.
axel.
Hi Rouhollah,
are the groups THERMO, NEWTON and nanoparticle in the LOADING section in your script non-overlapping?
Maybe some of the atoms in the group nanoparticle are time integrated by another integrator (fix nve and/or fix nvt), in addition to fix rigid.
Cheers,
-Trung