# question about "fix deform wiggle"

Dear all,

Dear all,

I'm wondering what I am doing is right when I use "fix deform wiggle".
I am confused about the frequency calculation.

for example:

units real
...
timestep 0.2
...
fix 4 all deform 1 xy wiggle 2 80 remap v

From the code above: the cycle is 80 fs, and the frequency is
1/(80e-15)=1.25e13, right?

And if it is right, I want to simulate in a low frequency, such as 10
hz, then I have to increase the value 80 to a very very large value,
which is very time-consuming.

80 Hz is not only time consuming, but in essence pointless for any
nanoscale (in size and time) simulation.
you can just as well assume the simulation cell is stationary.

axel.

fix 4 all deform 1 xy wiggle 2 80 remap v

In the manual, 80 reflects the period of oscillation (time units), it is not 80 Hz. What I am confused is how to compute the frequency?

Thank you!!!

my 80Hz are a typo. i meant 10Hz.

my statement stands: any deformation or manipulation frequency lower than, say, 1GHz is essentially pointless to simulate at the time and length scale available to atomic simulations and you can treat such systems as stationary.

you can figure this out easily from a back-of-the-envelope calculation.

axel.

I am just a beginner for LAMMPS.

So, please just tell me how to compute the frequency. Your help will be greatly appreciated!!!

``````<b>units real
...
timestep  0.2
...
fix        4 all deform 1 xy wiggle 2 80 remap v</b>
``````

Your calcualtion of what 80 fs means for frequency is correct.

If you wanted to cycle at 80 Hz, you would need

to simulate 1/80 s to be meaningful, which

is ~10^13 timesteps with a 1 fs step.

Axel is suggesting you canâ€™t realistically do that.

Steve