Author Topic: Questions about Eigenvectors  (Read 2977 times)

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Offline Fishpack

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Questions about Eigenvectors
« on: May 24, 2017, 12:49 »
I have calculated the eigenvectors of a graphene layer for phonon.
Successfully, I could obtain the eigenvector of the graphene layer at certain wave vectors.
(using the class of vibrational modes)
The output is arrays (that contains six elements) with six lines.
(Please, see the attached file)

I think the six lines is related on the phonon modes.
However, I don't know what the elements indicate.

In my opinion, for the graphene case, there are two eigenvector e1, e2.
Then, the six elements are e1x e1y e1z e2x e2y e2z.
Is that the correct? Please let me know about the eigenvector output.


Offline Petr Khomyakov

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Re: Questions about Eigenvectors
« Reply #1 on: May 26, 2017, 12:12 »
For a given k-point, I guess that the number of eigenvectors is the same as the number of phonon modes = 3xN, where N is the number of atoms in the unit cell you have adopted to calculate phonons in your system; the eigenvector dimension is given by the dimension of the Dynamical Matrix as briefly discussed in http://docs.quantumwise.com/manuals/Types/VibrationalMode/VibrationalMode.html.

If N=2, e.g., for the primitive cell of a single graphene sheet, the matrix dimension is then 6x6, meaning that each eigenvector has 6 elements.