CHECKPOINT FD: Difference between revisions

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{{DISPLAYTITLE:CHECKPOINT_FD}}
{{DISPLAYTITLE:CHECKPOINT_FD}}
{{TAGDEF|CHECKPOINT_FD|[string]}}
{{TAGDEF|CHECKPOINT_FD| CONTINUE {{!}} RESET {{!}} NONE {{!}} SINGLE | RESET}}


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


----
----
[[Phonons]] can be calculated using [[Phonons from finite differences | 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 {{TAG|CHECKPOINT_FD}} (with {{TAG|IBRION|6}}), it is possible to [[Construction:Restarting_finite_differences_calculations#Restarting_a_finite_difference_calculation | restart a calculation that crashed]] from the last displacement, or [[Construction:Restarting_finite_differences_calculations#Splitting_a_finite_difference_calculation | split the calculation into individual displacements]]. The displacements are written to the {{FILE|vaspcheckfd.h5}} file.
{{Available|6.6.0}}
{{Available|6.6.0}}
{{NB|important|This feature requires [[:Category:HDF5_support | HDF5 support]].}}
{{NB|important|This feature requires [[:Category:HDF5_support | HDF5 support]].}}
{{NB|mind|This is currently only available for {{TAG|IBRION|6}}.}}
{{NB|mind|This is currently only available for {{TAG|IBRION|6}}.}}
 
----
Phonon (or vibrational) modes can be calculated using [[Phonons from finite differences | 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 {{TAG|CHECKPOINT_FD}} (with {{TAG|IBRION|6}}), it is possible to [[Construction:Restarting_finite_differences_calculations#Restarting_a_finite_difference_calculation | restart a calculation that crashed]] from the last displacement, or [[Construction:Restarting_finite_differences_calculations#Splitting_a_finite_difference_calculation | split the calculation into individual displacements]]. The displacements are written to the {{FILE|vaspcheckfd.h5}} file.
=== {{TAG|CHECKPOINT_FD|CONTINUE}} ===
 
:The {{FILE|vaspcheckfd.h5}} file is read (if it exists) and the calculation continues where it left off. If the {{FILE|vaspcheckfd.h5}} file is missing, a {{FILE|vaspcheckfd.h5}} is created and the displacements are written to it. In both cases, the calculation will finish with the complete {{FILE|vaspcheckfd.h5}}. Repeating {{TAG|CHECKPOINT_FD|CONTINUE}} will perform a single SCF at the equilibrium structure and read the displacements from {{FILE|vaspcheckfd.h5}}.  
;{{TAG|CHECKPOINT_FD|CONTINUE}}  
: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.
*{{FILE|vaspcheckfd.h5}} file is read (if it exists) and the calculation continues where it left off.  
=== {{TAG|CHECKPOINT_FD|RESET}} (default) ===
*Otherwise, {{FILE|vaspcheckfd.h5}} is created and the displacements are written to it. In both cases, the calculation will finish with the complete {{FILE|vaspcheckfd.h5}}.  
*Repeating {{TAG|CHECKPOINT_FD|CONTINUE}} will perform a single SCF at the equilibrium structure and read the displacements from {{FILE|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.
;{{TAG|CHECKPOINT_FD|RESET}} - (default)
:Overwrite the {{FILE|vaspcheckfd.h5}} file and start from scratch. The rest is identical to {{TAG|CHECKPOINT_FD|CONTINUE}}.
:Overwrite the {{FILE|vaspcheckfd.h5}} file and start from scratch. The rest is identical to {{TAG|CHECKPOINT_FD|CONTINUE}}.
;{{TAG|CHECKPOINT_FD|NONE}}  
=== {{TAG|CHECKPOINT_FD|NONE}} ===
:Behavior of the code before VASP 6.6.0. No {{FILE|vaspcheckfd.h5}} file is written.
:No {{FILE|vaspcheckfd.h5}} file is written. This is the behavior of the code before VASP 6.6.0.
;{{TAG|CHECKPOINT_FD|PREPARE}}  
=== {{TAG|CHECKPOINT_FD|PREPARE}} ===
*The {{FILE|vaspcheckfd.h5}} file is created (or overwritten) and filled with metadata.  
:The {{FILE|vaspcheckfd.h5}} file is created (or overwritten) and filled with metadata. For each displacement, a {{FILE|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.  
*For each displacement, a {{FILE|CONTCAR_disp-N}} file is written containing the Nth displacement. VASP then stops after one SCF.  
:To run the calculation for a specific displacement, create a directory <code>disp-N</code>, copy across the corresponding {{FILE|CONTCAR_disp-N}} file and rename it to {{FILE|POSCAR}}. Then, run the calculation with {{TAG|CHECKPOINT_FD|SINGLE}}.
*To run this displaced calculation, create a directory ''disp-N'', copy across the corresponding {{FILE|CONTCAR_disp-N}} file into it and rename it to {{FILE|POSCAR}}. Then run the calculation with {{TAG|CHECKPOINT_FD|SINGLE}}.
=== {{TAG|CHECKPOINT_FD|SINGLE}} ===
;{{TAG|CHECKPOINT_FD|SINGLE}}  
:This mode is used to run the individual single-shot VASP calculations produced by {{TAG|CHECKPOINT_FD|PREPARE}}. This also produces a {{FILE|vaspcheckfd.h5}} file in the corresponding directory that contains the displaced data.
:This mode is used to run the individual single-shot VASP calculations produced by {{TAG|CHECKPOINT_FD|PREPARE}}. This also produces a {{FILE|vaspcheckfd.h5}} file in the corresponding directory that contains the displaced data.


Latest revision as of 14:12, 11 March 2026

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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