Dynamical Matrix

LAMMPS
1

Hello,

I apologize for this naive question, but I wanted to ensure I understood the LAMMPS documentation regarding the dynamical matrix calculation.

I couldn’t find any information related to the definition of the wave vector in the formulation shown in the documentation of the dynamical matrix. How are the wave vectors defined in LAMMPS?

I noticed something similar in the VASP documentation. Does LAMMPS handle this in a similar manner?

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Thank you very much for your elaboration in advance!

2

The formula for \Phi in the dynamical_matrix documentation seems clear enough to me. It’s simply the second derivative of energy with respect to the coordinates of atoms i and j (then scaled by square root of masses, multiplied).

Since LAMMPS represents atoms as points, the command does not directly do anything with wave vectors. You extract wave vectors yourself afterwards (by eigendecomposing the dynamical matrix or something – not my area of expertise).