[lammps-users] how to give shear?


Since Dinesh re-posted his query to the group, I would like to post
the following example which re-produces his problem. He apparently
works on a alloy system, but this input is for Ni using EAM potential.
Comparing it with the shear example shows that a "mobile" group is not
defined in this.
example. Hope this helps in understanding the error in the input file ..


in.dinesh (1.33 KB)

Hi Manoj
I have read your input script. But there is one thing unclear, can you help me figure out this question?
In your script

velocity upper set 1.0 0 0 units box
velocity upper ramp vx 0.0 1.0 y 12 20 sum yes units box

“velocity/set” can set a fixed velocity on a group of atoms from the beginning to the end.
“velocity/ramp” can make velocities ramped uniformly from vlo to vhi are applied to dimension vx, or vy, or vz.

Right here, you used both commands, what is the result?

PS: do you know how to apply external forces to a group of atoms, these forces ramped from flo to fhi?

Thank you so much.


Manoj Warrier <[email protected]…24…> д����

Hi Yang,

Please find attached an animated gif (19 KB only thanks to "xmovie"
and "convert") file which shows the result of using both "set" and
"ramp" for velocity. Note that in the shear example, the "set" and
"ramp" options act on different groups of atoms ("upper" group and
"mobile" group respectively).

I am sorry, but I have not applied an external force to a group of
atoms in lammps.

Best Regards,

2008/8/15 YANG LU <[email protected]>: