CHECKPOINT_FD

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CHECKPOINT_FD = CONTINUE | RESET | NONE | SINGLE
Default: CHECKPOINT_FD = RESET 

Description: Enables a finite differences calculation to be restarted or split up into displacements.

Phonons can be calculated using finite differences. A series of displacements is made, DFT calculations are performed on each of these, and then the second-order force constants are computed and the dynamical matrix constructed, from which the phonon modes and frequencies are calculated. Using CHECKPOINT_FD (with IBRION = 6), it is possible to restart a calculation that crashed from the last displacement, or split the calculation into individual displacements. The displacements are written to the vaspcheckfd.h5 file.

Mind: Available as of VASP 6.6.0
Important: This feature requires HDF5 support.
Mind: This is currently only available for IBRION = 6.

CHECKPOINT_FD = CONTINUE

The vaspcheckfd.h5 file is read (if it exists) and the calculation continues where it left off. If the vaspcheckfd.h5 file is missing, a vaspcheckfd.h5 is created and the displacements are written to it. In both cases, the calculation will finish with the complete vaspcheckfd.h5. Repeating CHECKPOINT_FD = CONTINUE will perform a single SCF at the equilibrium structure and read the displacements from vaspcheckfd.h5.
This mode also detects if the calculation is a single VASP calculation or if it was split into separate pieces. If it has been split, all the calculations need to have finished, or an error will be produced.

CHECKPOINT_FD = RESET (default)

Overwrite the vaspcheckfd.h5 file and start from scratch. The rest is identical to CHECKPOINT_FD = CONTINUE.

CHECKPOINT_FD = NONE

No vaspcheckfd.h5 file is written. This is the behavior of the code before VASP 6.6.0.

CHECKPOINT_FD = PREPARE

The vaspcheckfd.h5 file is created (or overwritten) and filled with metadata. For each displacement, a CONTCAR_disp-N file is written containing the Nth displacement. The calculation stops after performing one electronic minimization to obtain the SCF solution of the unperturbed structure.
To run the calculation for a specific displacement, create a directory disp-N, copy across the corresponding CONTCAR_disp-N file and rename it to POSCAR. Then, run the calculation with CHECKPOINT_FD = SINGLE.

CHECKPOINT_FD = SINGLE

This mode is used to run the individual single-shot VASP calculations produced by CHECKPOINT_FD = PREPARE. This also produces a vaspcheckfd.h5 file in the corresponding directory that contains the displaced data.

Related tags and articles

Phonons from finite differences, Restarting finite differences calculations, IBRION, vaspcheckfd.h5, CONTCAR_disp-N

Workflows that use this tag

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