K-Points: Use meshes with their origin at GAMA

2016-10-21

Mind: The division scheme (or the generating basis of the k-mesh) must lead to a k-mesh which belongs to the same class of Bravais lattice as the reciprocal unit cell (Brillouin zone). Any symmetry-breaking set-up of the mesh cannot be handled by VASP. Hence such set-ups are not allowed -- if you break this rule an error message will be displayed. Furthermore the symmetrisation of the k-mesh can lead to meshes which can not be divided into tetrahedrons (at least not by the tetrahedron division scheme implemented in VASP) -- if one uses meshes which do not have their origin at $ \Gamma $ (for certain lower symmetric types of Bravais lattices or certain non-symmetry conserving shifts). Therefore only very special shifts are allowed. If a shift is selected which can not be handled you get an error message. For reasons of safety it might be a good choice to use only meshes with their origin at $ \Gamma $ (switch 'G' or 'g' on third line or odd divisions) if the tetrahedron method is used.


From http://cms.mpi.univie.ac.at/vasp/vasp/Automatic_k_mesh_generation.html



hexagonal lattices

We strongly recommend to use only Gamma centered grids for hexagonal lattices. Many tests we have performed indicate that the energy converges significantly faster with $ \Gamma $ centered grids than with standard Monkhorst Pack grids. Grids generated with the ``M'' setting in the third line, in fact do not have full hexagonal symmerty.


from   http://cms.mpi.univie.ac.at/vasp/vasp/hexagonal_lattices.html


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