Quickstart: Parsing a VASP Calculation

Quickstart: Parsing a VASP Calculation#

This guide will walk you through a basic workflow: parsing eigenvalues from a VASP calculation output directory and saving them into a structured format.

1. Locate the Example Data#

dftio comes with example files for different DFT codes. For this guide, we will use the Gallium Arsenide (GaAs) example calculated with VASP, which is located in the example/vasp/GaAs/ directory.

This directory contains standard VASP output files:

  • OUTCAR

  • POSCAR

  • KPOINTS

  • EIGENVAL

2. Run the Parser#

We will use the dftio parse command to extract the electronic eigenvalues from these files. The command specifies the DFT code (vasp), the location of the data, and what we want to extract (--eigenvalue).

Open your terminal in the root of the dftio repository and run the following command:

dftio parse \
  --mode vasp \
  --root example/vasp/GaAs \
  --prefix "" \
  --outroot ./parsed_data \
  --eigenvalue

Let’s break down the command:

  • dftio parse: The command to run the parser.

  • --mode vasp: Specifies that we are parsing VASP output.

  • --root example/vasp/GaAs: The directory containing the VASP files.

  • --prefix "": Since VASP output files don’t share a common prefix (like frame_001, frame_002), we set this to an empty string. dftio will look for files like OUTCAR and EIGENVAL directly inside the --root directory.

  • --outroot ./parsed_data: The directory where the output will be saved.

  • --eigenvalue: A flag telling dftio to parse the eigenvalues and k-points.

3. Inspect the Output#

After the command finishes, a new directory named parsed_data will be created. Inside, you will find a file named 0.dat. This file contains the parsed data in a PyTorch-readable format.

The 0.dat file holds a Python dictionary containing:

  • kpoints: The coordinates of the k-points.

  • eigs: The eigenvalues for each band at each k-point.

  • weights: The weight of each k-point.

This file can now be easily loaded and used for further analysis or as input for a machine learning model. For example, to plot the band structure, you could use the dftio band command.

dftio band -r ./parsed_data

This command will generate a plot of the band structure from the parsed data.

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