A collection of scripts for converting output from the Vienna ab initio Simulation Package (VASP) to input for the General Utility Lattice Program (GULP).

Reads a VASP OUTCAR file, extracts various sets of data, and writes them to a GULP-friendly output format.

This script currently collects the following data:

• Structures with lattice vectors, atom types/positions, total energies, forces and stress tensors.
• Elastic-constant matrices.
• Phonon modes (frequencies and eigenvectors).

For single-point calculations, the script writes out the structure plus the total energy, gradients (minus forces) and strain derivatives (diagonal elements of the stress tensor).

For finite-differences calculations (e.g. IBRION = 6 with ISIF = 3), the script writes out the initial structure with the calculated elastic-constant matrix and/or phonon frequencies/eigenvectors, as well as each each of the intermediate structures with lattice distortions and atomic displacements.

Several optional command-line arguments allow the output to be customised - type python OUTCARToGULP.py -h for details, or look at the SrO/IBRION 6 example, which illustrates the basic usage of the script.

An auxiliary script for processing the VASP OUTCAR files generated from a sequence of single-point calculations for mapping a phonon-mode potential-energy surface using the ModeMap tool.

It can also be used to process similar calculations where multiple single-point calculations need to be performed (e.g. harmonic phonon calculations with the Phonopy code).

The script extracts the total energies, forces (gradients) and stress tensors (strain derivatives) from each structure and collects them into a single GULP-friendly output file.

It also accepts some of the same command-line arguments as OUTCARToGULP.py, which can be used to customise the output.

The usage of this script is illustrated by the ModeMap and Phonopy examples.