PHON BORN CHARGES: Difference between revisions

Latest revision as of 10:35, 23 October 2023

Default: PHON_BORN_CHARGES

= None

Description: PHON_BORN_CHARGES sets the Born effective charges to be used for the dipole-dipole corrections in the computation of the phonon dispersion. This is only used when LPHON_POLAR=.TRUE.

If the material is non-metallic and polar (i.e. two or more atoms in the unit cell carry nonzero Born effective charge tensors), a special treatment of the long-range dipole-dipole interaction is required to obtain a smooth phonon dispersion. This is activated by setting LPHON_POLAR=.TRUE. and supplying the static dielectric tensor (PHON_DIELECTRIC) and the Born-effective charges (PHON_BORN_CHARGES) which can be obtained in a separate VASP calculation using the LEPSILON or LCALCEPS tag. The dipole-dipole part of the interatomic force-constants is evaluated using an Ewald summation with the number of $\mathbf{G}$ vectors determined by the cutoff length (PHON_G_CUTOFF).

Mind: Only available as of VASP 6.3.2.

@@ Line 6: / Line 6: @@
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-If the material is polar (i.e. has more than one different atom type) a special treatment of the long-range dipole-dipole interaction is required to obtain a smooth phonon dispersion.
+If the material is non-metallic and polar (i.e. two or more atoms in the unit cell carry nonzero Born effective charge tensors), a special treatment of the long-range dipole-dipole interaction is required to obtain a smooth phonon dispersion.
-This is activated by setting {{TAG|LPHON_POLAR}}=.TRUE. and supplying the static dielectric tensor ({{TAG|PHON_DIELECTRIC}}) and the Born-effective charges ({{TAG|PHON_BORN_CHARGES}}) which can be obtained on a separate VASP run using the {{TAG|LEPSILON}} or {{TAG|LCALCEPS}} tag. The long-range part is evaluated using an Ewald sum with the number of G-vectors in reciprocal space being determined using a cutoff length ({{TAG|PHON_G_CUTOFF}}).
+This is activated by setting {{TAG|LPHON_POLAR}}=.TRUE. and supplying the static dielectric tensor ({{TAG|PHON_DIELECTRIC}}) and the Born-effective charges ({{TAG|PHON_BORN_CHARGES}}) which can be obtained in a separate VASP calculation using the {{TAG|LEPSILON}} or {{TAG|LCALCEPS}} tag.
+The dipole-dipole part of the interatomic force-constants is evaluated using an Ewald summation with the number of <math>\mathbf{G}</math> vectors determined by the cutoff length ({{TAG|PHON_G_CUTOFF}}).
 {{NB|mind| Only available as of VASP 6.3.2.}}

Latest revision as of 10:35, 23 October 2023

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