How to apply force

LAMMPS LAMMPS General Discussion
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Dear Experts,

I am modeling a cantilever fixed on the left side and free to move on the right side using LAMMPS. The cantilever is divided into three groups: (1) a short fixed group on the left, (2) a large middle group in the center, and (3) a short group at the tip. I apply a force using fix aveforce in the Z-axis (fix 9 tip_group aveforce NULL NULL -0.8) and run only one step to observe deflection and consequent damping in the cantilever. However, it does not seem that the cantilever behaves like a cantilever. its rather behaves like a rope! Is it because of the its size or the applied potential?!

It might be helpful to know, I used Tersoff potential for Si and applied fix nve and fix thermostat (temp/rescale) for the middle and tip groups, and do NOT turned them off when applying the load using fix 9.

Yours sincerely,
Bahman

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Both of these are testable hypotheses: you can work out the effect of cantilever length by building a smaller cantilever and you can work out the effect of applied potential by trying a different potential.

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I found out that! it is because of less amount of “moment of inertia” in smaller cross-section models…So, I must increase either the thickness of cantilever or its width to show sufficent regidity.

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