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# KPOINT BSE

From Vaspwiki

**KPOINT_BSE** = [integer] (optionally [integer],[integer],[integer])

Descprition: The flag **KPOINT_BSE** allows to calculate the dielectric matrix at one of the kpoints used to sample the Brillouin zone.

In the simplest form one can specify

KPOINT_BSE = index_of_k-point

It is best to select the desired k-point from the list of k-points in the OUTCAR file. Additionally a shift by an arbitrary reciprocal lattice vector can be supplied by specifying three additional integer numbers:

KPOINT_BSE = index_of_k-point n1 n2 n3

This allows the calculate the dielectric function at a k-point outside the first Brillouin zone corresponding to

where are the reciprocal lattice vectors of the unit cell.