Yambo Community Forum

Greetings all,

Just an hour ago, I computed the GW corrections for a graphene sheet and noticed that the kpoints generated in the NSCF Quantum Espresso output file and the QP's in Yambo are not the same. Specifically, the Dirac point is not the same XYZ as in the NSCF file. The index is the same in both output files. Under what conditions does Yambo alter the kpoints instead of evaluating/importing the exact kpoints as in the espresso output?

Regards

On closer look, it seems to be just a different coordinate system.

jmullen wrote:Under what conditions does Yambo alter the kpoints instead of evaluating/importing the exact kpoints as in the espresso output?

Dear Jeff, of course yambo does not alter the PW k-points list As you said it is only a matter of reference system. In yambo k-points coordinates are written in IKU=Internal K Units. Check any report file and search for


The IKU is simply obtained by applying the tranformation

(K1,K2,K3)_IKU=(Kx*2*pi/4.72,Kx*2*pi/4.08,Ky*2*pi/12.18)

It is simply a generalization of the 2*pi/alat used by PW. Note that the unit cell scaling factors are completely arbitrtary as they are internal to the code. They are simply used to have a more user friendly notation for the vectors in the Reciprocal lattice. So these factors can differ from the PW lattice constant. This is way, even in a cubic system, PW and yambo can print appraently different k-points.