[Pw_forum] What is the difference between Q points mesh and k points mesh

[Caloma Trumica]

Dear All,

I have a quick question:

When doing phonon calculation for a unit cell, we need to set up a qpoints
mesh. This mesh is built also based on M-K scheme, so the resulting
coordinates and weight should be exactly the same as those for k points if
the input grid is the same? say 5*5*5 for a cubic cell.

Is my understanding correct? If so, why do we need to have such an
additional setting of q points rather than just using k points mesh for
both?

Thanks.

Caloma Ditrica

PhD student from Penn State University
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