LPHON POLAR: Difference between revisions

Latest revision as of 14:55, 18 December 2024

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 $\mathbf{G}$ 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.

@@ Line 1: / Line 1: @@
 {{DISPLAYTITLE:LPHON_POLAR}}
-{{TAGDEF|LPHON_POLAR|.TRUE. {{!}} .FALSE. }}
+{{TAGDEF|LPHON_POLAR|.TRUE. {{!}} .FALSE.|.FALSE.}}
-{{DEF|LPHON_POLAR|.FALSE.|}}
-Description: {{TAG|LPHON_POLAR}} includes dipole-dipole corrections in the computation of the phonon dispersion. For this mode {{TAG|PHON_DIELECTRIC}}, {{TAG|PHON_BORN_CHARGES}} must also be set.
+Description: {{TAG|LPHON_POLAR}} includes dipole-dipole corrections in the computation of the phonon dispersion. For this mode, {{TAG|PHON_DIELECTRIC}} and {{TAG|PHON_BORN_CHARGES}} must also be set.
 ----
-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}}).
+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.}}

Latest revision as of 14:55, 18 December 2024

Related tags and articles