help to get natural frequency

Hello Everyone!

I want to simulate vibration of a nano plate with lammps software. would you
please guide me which command is suitable to get natural frequency ?
Also, if you know of any good paper/researcher for this QS, please let me know.
I am grateful to you if you give me guidance.

You could do a "fix setforce" to create a body force, and then put that in a loop that modifies by sin

something like this:

variable time index 1 2 3 4 ....314
variable W equal 1
label jumpHere
<some stuff>
fix forceID targetGroup setforce 0 0 sin(W*t)
<some more>
next time
jump jumpHere

That would drive the plate, and then you can modify W until you find some kind of resonance

Mohammad Athar
email: [email protected]

The first Q here is: do you know how to solve the problem in your head using pen and paper?
In general, natural frequencies are nothing but the eigenvalues (their square root to be more precise) of
the dynamical matrix or stiffness matrix or whatever you would like to call it depending on your background (chemistry,physics,engineering). Typically there are two ways to generate the matrix. In the first one, you expose the system
to a set of initial quasi-static displacements and from there you get the curvature of the energy landscape along each
direction, which is nothing but the directional stiffness. Covering all the representative directions allows you to
build the stiffness matrix. The second approach is to expose the system to a thermal bath and reconstruct the matrix employing
the perturbation-dissipation theorem. While the third proposed approach below by Mohammad is “theoretically” correct
and “maybe” an avenue for your particular system, I would say is the most unfeasible thing to be tried ever because among other things, to achieve resonance one needs to know not just the frequency but the shape of each oscillation mode and that my friend
is way too hard to guess for any non-trivial system geometry.
So try step one or two I have mentioned above. Those are your best bets for this type of calculation.