Can lammps calculate phonon spectra???

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1

Hello.

I need to simulate the phonon dispersion curves of bcc-Fe. Can lammps do this?
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2

I don’t know how this calculation is generally done. LAMMPS does
not do it directly - my guess is that this
is better as a post-processing task. Maybe someone
else can comment.

Steve

3

Sialon, as far as I know lammps does not do this directly, but it can be done by post-processing a dump file. See Lukes & Zhong, J. Heat Transfer 129(6) 2007 for the necessary theory.
Jeremy

4

Jeremy and Sialon,

As far as I know, what have done in Lukes & Zhong’s paper is plotting phonon density of state not dispersion curve via fast Fourier transformation of velocity auto-correlation (common method). For CNT, to obtain the dispersion curve, one can basically get the phonon dispersion curve by manupilating the velocity of atoms. Then one may need some knowledge on lattice dynamics to get the dispersion curve by connecting these discrete points to be lines in dispersion curve.

I’m not sure how to do with bulk materials like bcc-Fe. What people usually do with ab initio is first get the force on each atoms in the unit cell, and diagonalize the lattice dynamic matrix to get the eigenvalues. This requires some sort of post-processing. I’m sure the paper publishing the potential should have the info of dispersion curves therein.

Best,

Ajing