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Hi,
I’m trying to calculate the band structure of a ZnO N-doped system.
I don`t have too experience and I have some questions.
1. When I calculate the geometry optimization and make a calculation with ISIF= 3 the cell volume decrease, but if I make the calculation with ISIF = 2 or 4 I can’t know which is the nitrogen influence in the cell parameters and volume.
2. Moreover, I never make a band structure calculation. I need the KPOINTS for a hexagonal cell, but I don’t know how I can do it.
Thank you in advance

1) please keep in mind that your cell size of the calculation corresponds to a very high dopant concentration: (a few percent or a few tenth of a percent). I am not sure about dopant concentrations in real ZnO-specimen, but they might be much lower. Hence the volume effect of the dopants might be vanishingly small in the real crystal and thus severely overestimated if you do a fulll volume relaxation of your unit cell.
2)insert the dopant such that the hexagonal symmetry is preserverd!
then
-- if you use vasp.4.6, please use the format of KPOINTS which is given in example 2_3 of the vasp-workshop excercises (Handson2.tgz on http://cms.mpi.univie.ac.at/vasp-workshop) and adapt the lines for the high-symmetry directions in a hexagonal BZ which are usually given in band-structure plots. (I am sure there are several band structures published even for for ZnO)
-- if you use hybrid functionals, first generate the appropriate k-mesh (IBZKPT ) by running vasp.4.6 (until this file is written) without using hybrid functionals,
then please proceed as discussed in this forum, and add those k-points which have been obtained in IBZKPT in the KPOINTS file
[ Edited Mon Jul 19 2010, 02:20PM ]