PHON G CUTOFF: Difference between revisions
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{{DEF|PHON_G_CUTOFF|None|}} | {{DEF|PHON_G_CUTOFF|None|}} | ||
Description: {{TAG|PHON_G_CUTOFF}} sets the cutoff radius in reciprocal space used to determine the number of G | Description: {{TAG|PHON_G_CUTOFF}} sets the cutoff radius in reciprocal space used to determine the number of <math>\mathbf{G}</math> vectors involved in the Ewald sum in polar phonon calculations. | ||
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If the material is polar (i.e. has more than one | If the material is polar (i.e. has more than one atom type), 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 | 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 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}}). | ||
{{NB|mind| Only available as of VASP 6.3.2.}} | {{NB|mind| Only available as of VASP 6.3.2.}} | ||
Revision as of 09:40, 20 July 2022
PHON_G_CUTOFF = [3x3xNIONS real]
| Default: PHON_G_CUTOFF | = None |
Description: PHON_G_CUTOFF sets the cutoff radius in reciprocal space used to determine the number of [math]\displaystyle{ \mathbf{G} }[/math] vectors involved in the Ewald sum in polar phonon calculations.
If the material is polar (i.e. has more than one atom type), 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 long-range part is evaluated using an Ewald sum with the number of [math]\displaystyle{ \mathbf{G} }[/math] vectors in reciprocal space being determined using a 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_DIELECTRIC, PHON_BORN_CHARGES