# How do I extract the wave function from a VASP calculation?

We can obtain a energy band structure of a crystal from a DFT calculation in Vasp. Each point in each band represents an energy eigenvalue with a corresponding wave function from the Schrödinger equation. I want to choose a specific K-point in the Brillouin zone for a specific band and investigate the symmetry of the corresponding wave function.

Supposedly, I can obtain the wave function from the WAVECAR file. It should yield a number of coefficients which can be used to construct the wave function from the basis functions used in the calculations. However, I do not need the full wave function. I only want to know the symmetry of the function. If my basis was small, I could easily identify the symmetry by inspection, but with hundreds (?) of coefficients this seems difficult.

How can I find the symmetry of the wave function from my VASP calculation? Please, also let me know if it seems like I am asking the wrong question.

• +1. I've just made some edits to make the "question" part of your post standout more, and used a code block for WAVECAR. Also we have a VASP chat room. Please stop by and write "hello" there so that we remember you when there's any announcement or discussion about VASP which may be interesting for VASP users! Mar 25 '21 at 15:42
• You may take a look at this: andrew.cmu.edu/user/feenstra/wavetrans
– Jack
Mar 26 '21 at 6:13

## 1 Answer

It seems you are looking for a package to compute the irreducible representation of electronic states computed by VASP. This has been recently developed:

J. Gao J, Wu Q, Persson C, Z. Wang. Irvsp: to obtain irreducible representations of electronic states in the VASP. Comput. Phys. Comm. 261, 107760 (2021). https://doi.org/10.1016/j.cpc.2020.107760.

And the code is provided on github: https://github.com/zjwang11/irvsp