LCALCEPS: Difference between revisions

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where, by default, VASP chooses <span style="font-size:16pt">''&epsilon;''</span><sub>x</sub>=<span style="font-size:16pt">''&epsilon;''</span><sub>y</sub>=<span style="font-size:16pt">''&epsilon;''</span><sub>z</sub>=0.01 eV/&Aring;.
where, by default, VASP chooses <span style="font-size:16pt">''&epsilon;''</span><sub>x</sub>=<span style="font-size:16pt">''&epsilon;''</span><sub>y</sub>=<span style="font-size:16pt">''&epsilon;''</span><sub>z</sub>=0.01 eV/&Aring;.
This default may be overwritten by specifying
{{TAG|EFIELD_PEAD}}= <span style="font-size:16pt">''&epsilon;''</span><sub>x</sub> <span style="font-size:16pt">''&epsilon;''</span><sub>y</sub> <span style="font-size:16pt">''&epsilon;''</span><sub>z</sub>
in the {{FILE|INCAR}} file.


== Related Tags and Sections ==
== Related Tags and Sections ==

Revision as of 16:12, 19 March 2011

LCALCEPS = .TRUE. | .FALSE.
Default: LCALCEPS = .FALSE. 

Description: for LCALCEPS=.TRUE. the macroscopic ion-clamped static dielectric tensor, Born effective charge tensors, and the ion-clamped piezoelectric tensor of the system are determined from the response to finite electric fields.


For LCALCEPS=.TRUE., VASP calculates the ion-clamped static dielectric tensor

the Born effective charge tensors

and the ion-clamped piezoelectric tensor of the system

from the self-consistent response to a finite electric field ε. In this case, the "response" of the system is the change in the polarization P, the Hellmann-Feynman forces F, and the stress tensor σ.

To this end VASP will perform essentially three successive calculations, with:

EFIELD_PEAD= εx 0 0
EFIELD_PEAD= 0 εy 0
EFIELD_PEAD= 0 0 εz 

where, by default, VASP chooses εx=εy=εz=0.01 eV/Å.

This default may be overwritten by specifying

EFIELD_PEAD= εx εy εz

in the INCAR file.

Related Tags and Sections

LEPSILON, LCALCPOL, EFIELD_PEAD, LPEAD, IPEAD, LBERRY, IGPAR, NPPSTR, DIPOL, Berry phases and finite electric fields


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