POTIM: Difference between revisions

Revision as of 09:35, 8 August 2019

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 fs) 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

IBRION, NFREE

Examples that use this tag

@@ Line 3: / Line 3: @@
 {{DEF|POTIM|none,| ''must'' be set if {{TAG|IBRION}}{{=}} 0 (MD)|0.5| if {{TAG|IBRION}}{{=}} 1,2,3 (ionic relaxation) and 5 (up to VASP.4.6)|0.015|for {{TAG|IBRION}}{{=}}5 (up from VASP.5.1)}}
-Description: time (MD) or step width scaling (ionic relaxations) constant
+Description: {{TAG|POTIM}} sets the time step (MD) or step width scaling (ionic relaxations).
 ----
 <span>
-{{TAG|IBRION}} = 0 :
+{{TAG|IBRION}} = 0:
-:{{TAG|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.
+:{{TAG|POTIM}} gives the time step (in fs) in all ab-initio Molecular Dynamics runs, it ''has'' to be supplied therefore, otherwise VASP crashes immediately after having started.
 </span>
 <span>
-{{TAG|IBRION}} =1,2,3
+{{TAG|IBRION}} =1,2,3:
-:in all minimization algorithms (quasi-Newton, conjugate gradient, and damped molecular dynamics)  {{TAG|POTIM}} serves as a scaling constant for the step widths. Especially the Quasi-Newton algorithm is sensitive to the choice of this parameter
+:In all minimization algorithms (quasi-Newton, conjugate gradient, and damped molecular dynamics)  {{TAG|POTIM}} serves as a scaling constant for the step widths. Especially the Quasi-Newton algorithm is sensitive to the choice of this parameter.
 </span>
 <span>
-{{TAG|IBRION}} = 5 (6)
+{{TAG|IBRION}} = 5,6:
-:in frozen phonon calculations, {{TAG|POTIM}} gives the width of the displacement of each ion to calculate the Hessian Matrix.
+:In frozen phonon calculations, {{TAG|POTIM}} gives the width of the displacement of each ion to calculate the Hessian Matrix.
 :'''VASP.4.6''' and older releases: {{TAG|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  {{TAG|POTIM}} is unreasonably large, {{TAG|POTIM}} is automatically reset to 0.015&Aring;
+:'''VASP.5.1''' and newer releases: if the supplied value for  {{TAG|POTIM}} is unreasonably large, {{TAG|POTIM}} is automatically reset to 0.015 &Aring;.
 </span>
+== Related Tags and Sections ==
+{{TAG|IBRION}}, {{TAG|NFREE}}
+{{sc|POTIM|Examples|Examples that use this tag}}
 ----
-== Related Tags and Sections ==
-{{TAG|IBRION}}, ({{TAG|NFREEE}})
-[[The_VASP_Manual|Contents]]
+[[Category:INCAR]][[Category:Structural Optimization]][[Category:Molecular Dynamics]][[Category:Ionic Minimization Methods]][[Category:Lattice Vibrations]][[Category:Phonons]]