Output Files

In addition to ASE (described below), the official  py4vasp  Python package can be used to automatically parse most VASP output parameters.  🧞⁠⁠Pymatgen⁠  also has  several utilities  for VASP output parsing.

OUTCAR

Overview


OUTCAR
820KB, Uploaded 2 years ago
The primary output file in VASP is called the OUTCAR file. There is a ton of info in it. Here are the most important things:
  • Iteration: This line specifies the iteration of the geometry optimization procedure and the SCF loop for that given geometry. A value of Iteration      4(   2) would indicate "geometry step 4, SCF iteration 2."
  • energy(sigma->0): The value following this line is the current iteration's energy. The unit is eV.
  • magnetization (x): If LORBIT is set to >= 11, the atom-wise spin moments are printed in this table, each in units of Bohr-magnetons.
You can also use ASE to easily parse the most critical information (i.e. energy, forces, trajectory) from the OUTCAR as follows:
from ase.io import read

trajectory = read("OUTCAR", index=":") # list[Atoms]
final_image = trajectory[-1]
final_energy = final_image.get_potential_energy()
final_forces = final_image.get_forces()

Live Monitoring

It is often useful to monitor the progress of a calculation in real-time. This can be done using the grad2 utility, which is included below and is also added to your PATH on the Princeton Research Computing machines.

grad2
6KB, Uploaded 2 years ago
When you want to monitor a calculation, run grad2 OUTCAR from the command-line in any directory containing the OUTCAR you want to monitor.
The output looks like the following:
1  Energy:  -725.474813  Log|dE|:  2.861  SCF:  12  Avg|F|:  0.146  Max|F|:  0.247  Vol.: 4326.3  Time:  0.23m
2  Energy:  -725.349355  Log|dE|: -0.902  SCF:  12  Avg|F|:  0.522  Max|F|:  1.010  Vol.: 4394.4  Time:  0.23m
3  Energy:  -725.532040  Log|dE|: -0.738  SCF:  15  Avg|F|:  0.123  Max|F|:  0.218  Vol.: 4350.6  Time:  0.31m
4  Energy:  -725.559079  Log|dE|: -1.568  SCF:  12  Avg|F|:  0.182  Max|F|:  0.389  Vol.: 4396.4  Time:  0.23m
5  Energy:  -725.570525  Log|dE|: -1.941  SCF:  10  Avg|F|:  0.115  Max|F|:  0.226  Vol.: 4380.1  Time:  0.19m
Do not use the energy from grad2 for generating results and figures. The energy here is the force-consistent energy, whereas the energy used for any type of analysis is the energy(sigma->0) value. The energy(sigma->0) value is the one returned by ASE's .get_potential_energy() function.

CONTCAR

The CONTCAR file is formatted identically as the POSCAR file but contains the most recent set of atomic positions and cell parameters. You can view the CONTCAR and POSCAR in programs like VESTA or ASE. When restarting a calculation, you can copy the mv CONTCAR POSCAR to continue the geometry optimization process.

Volumetric Files

  • CHGCAR: If LCHARG = .TRUE., the charge density will be written out in this file.
  • WAVECAR: If LWAVE = .TRUE., the wavefunction will be written out in this file. This is particularly useful when restarting calculations, as they will automatically read this file.

Other Files

  • DOSCAR: Data about the density of states.
  • EIGENVAL: Data about the Kohn-Sham eigenvalues.
  • OSZICAR: Contains data for each SCF iteration. Useful for identifying SCF convergence issues. This is the energy data displayed via the grad2 utility.