Dear all,

I've been trying and struggling to obtain a (time dependent) 3d displacement field of an fcc crystal in the k space.

Since the lattice structure is not regular (unlike a simple cubic one), I’m having troubles in Fourier transforming the displacement field into the k-space in the post processing.

Additionally, it seems the “dump h5md” command does not store the information of the ordering of the atoms, which makes the whole analysis very tedious to begin with.

So, I’d like to know if there’s a lammps command to directly calculate a 3d displacement field of any crystal structure in the k space.

It seems it should be possible as lammps should calculate this quantity to calculate the dynamical matrix or phonon frequencies.

In fact, the best would be to obtain the displacement field in the k-omega space.

If this is not implemented, I’d like to know how to properly store the displacement field (or the positions of atoms) in a orderly manner,

so that I can easily post process the raw data to obtain the k-space counterpart.

Thanks in advance

Best,

P.S. Here I attach a video showing the time dependent displacement field, if this helps.

I want to transform this data into the k-omega space.

3d-field-animated0.mp4 (274 KB)