POTIM
POTIM = [real]
| Default: POTIM | = none, | must be set if IBRION= 0 (MD) |
| = 0.5 | if IBRION= 1,2,3 (ionic relaxation) and 5 (up to VASP.4.6) | |
| = 0.015 | for IBRION=5 (up from VASP.5.1) |
Description: POTIM sets the time step (MD) or step width scaling (ionic relaxations).
IBRION = 0:
- POTIM gives the time step in all ab-initio Molecular Dynamics runs, it has to be supplied therefore, otherwise VASP crashes immediately after having started.
IBRION =1,2,3:
- In all minimization algorithms (quasi-Newton, conjugate gradient, and damped molecular dynamics) POTIM serves as a scaling constant for the step widths. Especially the Quasi-Newton algorithm is sensitive to the choice of this parameter
IBRION = 5,6:
- In frozen phonon calculations, POTIM gives the width of the displacement of each ion to calculate the Hessian Matrix.
- VASP.4.6 and older releases: POTIM has to be small enough to ensure that the displacements are within the harmonic limit. The vibrational frequencies using the frozen phonon approach are based on the harmonic approximation.
- VASP.5.1 and newer releases: if the supplied value for POTIM is unreasonably large, POTIM is automatically reset to 0.015 Å.
Related Tags and Sections
Example Calculations using this Tag
Alpha-AlF3, Alpha-SiO2, CO on Ni 111 surface, CO vibration, Collective jumps of a Pt adatom on fcc-Pt (001): Nudged Elastic Band Calculation, Constrained MD using a canonical ensemble, Constrained MD using a microcanonical ensemble, H2O molecular dynamics, H2O vibration, liquid Si, Ni 100 surface relaxation, Relaxed geometry, Standard relaxation, TS search using the Improved Dimer Method, TS search using the NEB Method, Vibrational Analysis of the TS