PHON DIELECTRIC: Difference between revisions

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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 <math>\mathbf{G}</math> 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.}}
{{NB|mind| Only available as of VASP 6.3.2.}}



Latest revision as of 10:35, 23 October 2023

PHON_DIELECTRIC = [3x3 real] 

Default: PHON_DIELECTRIC = None

Description: PHON_DIELECTRIC sets the static dielectric tensor 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 vectors determined by the cutoff length (PHON_G_CUTOFF).

Mind: Only available as of VASP 6.3.2.

Related tags and articles

QPOINTS, LPHON_DISPERSION, PHON_NWRITE, LPHON_POLAR, PHON_BORN_CHARGES, PHON_G_CUTOFF

Examples that use this tag