LCALCPOL: Difference between revisions

From VASP Wiki
No edit summary
 
(11 intermediate revisions by 3 users not shown)
Line 5: Line 5:
For {{TAG|LCALCPOL}}=.TRUE., VASP calculates the electronic contribution to the polarization, along the three reciprocal lattice vectors '''G'''<sub>i</sub>, i=1,2,3,  (i.e. &Sigma;<sub>i</sub> '''P'''&middot;'''G'''<sub>i</sub>) in a single run (unlike {{TAG|LBERRY}}=.TRUE.).
For {{TAG|LCALCPOL}}=.TRUE., VASP calculates the electronic contribution to the polarization, along the three reciprocal lattice vectors '''G'''<sub>i</sub>, i=1,2,3,  (i.e. &Sigma;<sub>i</sub> '''P'''&middot;'''G'''<sub>i</sub>) in a single run (unlike {{TAG|LBERRY}}=.TRUE.).


== Related Tags and Sections ==
=== An example: The fluorine displacement dipole (Born effective charge) in NaF ===
 
*With {{FILE|INCAR}} file:
 
{{TAGBL|PREC}} = Med
{{TAGBL|EDIFF}}= 1E-6
{{TAGBL|ISMEAR}} = 0
{{TAGBL|DIPOL}}  = 0.25 0.25 0.25
{{TAGBL|LCALCPOL}} = .TRUE.
 
*{{FILE|KPOINTS}} file:
 
6x6x6
  0
Gamma
  6 6 6
  0 0 0
 
*{{FILE|POSCAR}} file:
 
NaF
  4.5102
  0.0 0.5 0.5
  0.5 0.0 0.5
  0.5 0.5 0.0
1 1
Direct
  0.0000000000000000  0.0000000000000000  0.0000000000000000
  0.5000000000000000  0.5000000000000000  0.5000000000000000
 
*and LDA Na_sv and F PAW datasets.
 
The {{FILE|OUTCAR}} file should now contain the following lines:
 
            Ionic dipole moment: p[ion]=(    2.25510    2.25510    2.25510 ) electrons Angst
  Total electronic dipole moment: p[elc]=(    0.00000    0.00000    0.00000 ) electrons Angst
Here the units "electrons Angst" denote <math>e\AA=-1.602 10^{-19}C\AA</math>.
 
To calculate the change in the electronic polarization of NaF due to the displacement of the fluorine sublattice we repeat the previous calculation with the following {{FILE|POSCAR}} file:
 
NaF
  4.5102
  0.0 0.5 0.5
  0.5 0.0 0.5
  0.5 0.5 0.0
1 1
Direct
  0.0000000000000000  0.0000000000000000  0.0000000000000000
  0.5100000000000000  0.5100000000000000  0.4900000000000000
 
The {{FILE|OUTCAR}} should now contain something very similar to the following lines:
 
            Ionic dipole moment: p[ion]=(    2.25510    2.25510    1.93939 ) electrons Angst
  Total electronic dipole moment: p[elc]=(    0.00000    0.00000    0.36061 ) electrons Angst
 
From the above one easily recognizes that the change in the electronic dipole moment due to the F-sublattice displacement is:
 
<math>\Delta\mathrm{p[elc]}=0.3606\hat{z}\;e\AA</math>
 
and the corresponding change in the ionic dipole moment:
 
<math>\Delta\mathrm{p[ion]}=1.93939-2.25510=-0.31571\hat{z}\;e\AA</math>
 
Thus the total change is found to be:
 
<math>\Delta\mathrm{p[tot]}=0.36061-0.31571=0.0449\hat{z}\;e\AA</math>
 
and considering that the F-sublattice was displaced by 0.045102 &Aring; these calculations yield a Born effective charge for fluorine of
 
<math>Z^*=0.0449/0.045102=-0.995|e|\;</math>.
 
The socalled parallel or <math>\bold{G}_{\parallel}</math>
direction in the integration over the reciprocal space unit cell is set in {{TAG|IGPAR}}.
 
== Related tags and articles ==
{{TAG|LCALCEPS}},
{{TAG|LCALCEPS}},
{{TAG|EFIELD_PEAD}},
{{TAG|EFIELD_PEAD}},
Line 15: Line 93:
{{TAG|DIPOL}},
{{TAG|DIPOL}},
[[Berry_phases_and_finite_electric_fields|Berry phases and finite electric fields]]
[[Berry_phases_and_finite_electric_fields|Berry phases and finite electric fields]]
{{sc|LCALCPOL|Examples|Examples that use this tag}}
----
----
[[The_VASP_Manual|Contents]]


[[Category:INCAR]][[Category:Berry phases]]
[[Category:INCAR tag]][[Category:Linear response]][[Category:Dielectric properties]][[Category:Berry phases]]

Latest revision as of 07:58, 19 July 2022

LCALCPOL = .TRUE. | .FALSE.
Default: LCALCPOL = .FALSE. 

Description: LCALCPOL=.TRUE. switches on the evaluation of the Berry phase expressions for the macroscopic electronic polarization in accordance with the so-called Modern Theory of Polarization.


For LCALCPOL=.TRUE., VASP calculates the electronic contribution to the polarization, along the three reciprocal lattice vectors Gi, i=1,2,3, (i.e. Σi P·Gi) in a single run (unlike LBERRY=.TRUE.).

An example: The fluorine displacement dipole (Born effective charge) in NaF

PREC = Med
EDIFF= 1E-6

ISMEAR = 0
DIPOL  = 0.25 0.25 0.25

LCALCPOL = .TRUE.
6x6x6
 0
Gamma
 6 6 6
 0 0 0
NaF
 4.5102
 0.0 0.5 0.5
 0.5 0.0 0.5
 0.5 0.5 0.0
1 1
Direct
  0.0000000000000000  0.0000000000000000  0.0000000000000000
  0.5000000000000000  0.5000000000000000  0.5000000000000000
  • and LDA Na_sv and F PAW datasets.

The OUTCAR file should now contain the following lines:

            Ionic dipole moment: p[ion]=(     2.25510     2.25510     2.25510 ) electrons Angst

 Total electronic dipole moment: p[elc]=(     0.00000     0.00000     0.00000 ) electrons Angst

Here the units "electrons Angst" denote .

To calculate the change in the electronic polarization of NaF due to the displacement of the fluorine sublattice we repeat the previous calculation with the following POSCAR file:

NaF
 4.5102
 0.0 0.5 0.5
 0.5 0.0 0.5
 0.5 0.5 0.0
1 1
Direct
  0.0000000000000000  0.0000000000000000  0.0000000000000000
  0.5100000000000000  0.5100000000000000  0.4900000000000000

The OUTCAR should now contain something very similar to the following lines:

            Ionic dipole moment: p[ion]=(     2.25510     2.25510     1.93939 ) electrons Angst

 Total electronic dipole moment: p[elc]=(     0.00000     0.00000     0.36061 ) electrons Angst

From the above one easily recognizes that the change in the electronic dipole moment due to the F-sublattice displacement is:

and the corresponding change in the ionic dipole moment:

Thus the total change is found to be:

and considering that the F-sublattice was displaced by 0.045102 Å these calculations yield a Born effective charge for fluorine of

.

The socalled parallel or direction in the integration over the reciprocal space unit cell is set in IGPAR.

Related tags and articles

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

Examples that use this tag