Yambo k points from quantum espresso

[jmullen]

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

[jmullen]

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

[andrea marini]

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

Code: Select all

 Unit cell scaling factors [a.u.]:  4.71637   4.08450  12.17584

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.