DIPOL: Difference between revisions

Revision as of 17:39, 29 August 2012

(VASP.3.2 only)
DIPOL = [real array]
Default: DIPOL = Template:FIXME

For VASP.4.X behavior please refer to Monopole, Dipole and Quadrupole corrections.

It is possible to calculate the total dipole-moment in the cell, using the option

DIPOL=R_x R_y R_z

where R_x, R_y and R_z specify the center of the cell in direct lattice coordinates.

Mind: the calculation of the dipole requires a definition of the center of the cell, and results might differ for different positions. You should use this option only for surfaces and isolated molecules. In this case use the center of mass for the position (for surface only the component normal to the surface is meaningful).

The main problem is that the definition of the dipole 'destroys' the translational symmetry, i.e. the dipole is defined as

{\displaystyle \int ({\mathbf r}-{\mathbf R}_{\rm center}) \rho_{\rm ions+valence}{\mathbf r} d^3 {\mathbf r}. }

Now, this makes only sense if $\rho_{\rm ions+valence}$ drops to zero at some distance from $\mathbf R_{\rm center}$ . If this is not the case, the values are extremely sensible with respect to changes in $\mathbf R_{\rm center}$ .

@@ Line 1: / Line 1: @@
-{{TAGDEF|DIPOL|[real array]|{{FIXME|default none or the origin 0 0 0}}|(VASP.3.2 only)}}
+(VASP.3.2 only)<br />
+{{TAGDEF|DIPOL|[real array]|{{FIXME|default none or the origin 0 0 0}}|}}
 For VASP.4.X behavior please refer to [[Monopole_Dipole_and_Quadrupole_corrections|Monopole, Dipole and Quadrupole corrections]].
 It is possible to calculate the total dipole-moment in the cell, using the option
-  {{TAG|DIPOL}}=<span style="font-size:16pt">''R''</span><sub>x</sub> <span style="font-size:16pt">''R''</span><sub>y</sub> <span style="font-size:16pt">''R''</span><sub>z</sub>
+  {{TAG|DIPOL}}='''R'''<sub>x</sub> '''R'''<sub>y</sub> '''R'''<sub>z</sub>
+where '''R'''<sub>x</sub>, '''R'''<sub>y</sub> and '''R'''<sub>z</sub> specify the center of the cell in direct lattice coordinates.
 ----
 Mind: the calculation of the dipole requires a definition of the center of the cell, and results might differ for different positions.
@@ Line 16: / Line 18: @@
 </math>
-Now, this makes only sense if <math>\rho_{\rm ions+valence}</math> drops to zero at some distance from <math>R_{\rm center}</math>. If this is
+Now, this makes only sense if <math>\rho_{\rm ions+valence}</math> drops to zero at some distance from <math>\mathbf R_{\rm center}</math>. If this is
-not the case, the values are extremely sensible with respect to changes in <math>R_{\rm center}</math>.
+not the case, the values are extremely sensible with respect to changes in <math>\mathbf R_{\rm center}</math>.