LPHON POLAR: Difference between revisions
No edit summary |
No edit summary |
||
| Line 6: | Line 6: | ||
---- | ---- | ||
If the material is polar (i.e. | 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 in a separate VASP calculation using the {{TAG|LEPSILON}} or {{TAG|LCALCEPS}} tag. | 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}}). | 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}}). | ||
In the case of metals, the dielectric function is infinite, for nonpolar semiconductors the Born effective charges are zero which in both cases means that the [[Phonons:_Theory#Long-range_interatomic_force_constants_.28LO-TO_splitting.29|long-range interatomic force-constants]] are zero and this dipole-dipole correction does not need to be applied. | |||
{{NB|mind| Only available as of VASP 6.3.2.}} | {{NB|mind| Only available as of VASP 6.3.2.}} | ||
Revision as of 10:33, 23 October 2023
LPHON_POLAR = .TRUE. | .FALSE.
| Default: LPHON_POLAR | = .FALSE. |
Description: LPHON_POLAR includes dipole-dipole corrections in the computation of the phonon dispersion. For this mode, PHON_DIELECTRIC and PHON_BORN_CHARGES must also be set.
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).
In the case of metals, the dielectric function is infinite, for nonpolar semiconductors the Born effective charges are zero which in both cases means that the long-range interatomic force-constants are zero and this dipole-dipole correction does not need to be applied.
| Mind: Only available as of VASP 6.3.2. |
Related tags and articles
QPOINTS, LPHON_DISPERSION, PHON_NWRITE, PHON_DIELECTRIC, PHON_BORN_CHARGES, PHON_G_CUTOFF