LCALCPOL: Difference between revisions

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 G_i, i=1,2,3, (i.e. Σ_i P·G_i) in a single run (unlike LBERRY=.TRUE.).

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

With INCAR file:

PREC = Med
EDIFF= 1E-6

ISMEAR = 0
DIPOL  = 0.25 0.25 0.25

LCALCPOL = .TRUE.

KPOINTS file:

6x6x6
 0
Gamma
 6 6 6
 0 0 0

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 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 $e\AA=-1.602 10^{-19}C\AA$ .

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:

$\Delta\mathrm{p[elc]}=0.3606\hat{z}\;e\AA$

and the corresponding change in the ionic dipole moment:

$\Delta\mathrm{p[ion]}=1.93939-2.25510=-0.31571\hat{z}\;e\AA$

Thus the total change is found to be:

$\Delta\mathrm{p[tot]}=0.36061-0.31571=0.0449\hat{z}\;e\AA$

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

$Z^*=0.0449/0.045102=-0.995|e|\;$ .

The socalled parallel or $\bold{G}_{\parallel}$ direction in the integration over the reciprocal space unit cell is set in IGPAR.

@@ 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.).
-An example: '''The fluorine displacement dipole (Born effective charge) in NaF'''.
+=== An example: The fluorine displacement dipole (Born effective charge) in NaF ===
 *With {{FILE|INCAR}} file:
-  PREC = Med
+  {{TAGBL|PREC}} = Med
-  EDIFF= 1E-6
+  {{TAGBL|EDIFF}}= 1E-6
-  ISMEAR = 0
+  {{TAGBL|ISMEAR}} = 0
-  DIPOL  = 0.25 0.25 0.25
+  {{TAGBL|DIPOL}}  = 0.25 0.25 0.25
-  LCALCPOL = .TRUE.
+  {{TAGBL|LCALCPOL}} = .TRUE.
 *{{FILE|KPOINTS}} file:
@@ Line 44: / Line 44: @@
    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:
@@ Line 75: / Line 76: @@
 <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 ''Z''<sup>*</sup>=0.0449/0.045102= -0.995.
+and considering that the F-sublattice was displaced by 0.045102 &Aring; these calculations yield a Born effective charge for fluorine of
-== Related Tags and Sections ==
+<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|EFIELD_PEAD}},
@@ Line 87: / Line 93: @@
 {{TAG|DIPOL}},
 [[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]]