VASP Forum

HI all, I am getting the infamous

VERY BAD NEWS! internal error in subroutine IBZKPT:
Reciprocal lattice and k-lattice belong to different class of lattices. Often results are still useful..

error. While I do understand why it arises, I still do not understand how to rectify it. WHat's wrong with my KPOINT file that causes this error in frequency calculations (but not geometry optimization)?

see attached and thank you

Jonas

Hi Jonas,

Thanks for reaching out. Since you have a triclinic cell, you can enter something like

this makes the warning go away
0
Gamma
8 7 5

in your KPOINTS file. However, this error is really not an error but rather a warning. In newer versions of VASP, your example simply runs without issuing the warning and it will produce good results regardless.

Alternatively, you can also increase the symmetry of your simulation cell from triclinic to orthorhombic and the warning should also disappear.

However, there are some real issues that I have encountered while looking at your input file:

• LADDGRID is not an INCAR tag, use ADDGRID instead.

• NCORE parallelism is currently not supported with IBRION=5/6. This causes your calculation to crash.