Hi QE users! I am studying the effect of the strain over the eigenvalues of VBM and CBM levels, my system is a cubic metal oxide semiconductor. My doubt born about the fact: V(G=0) = (1/V) sum sub u alpha sub u When I change the cell constant, the volume change, but not the alphas, because i use the same number, type and pseudopotential for atoms. Then the change in V(G=0) is only for the volume change. I think that in order to compare the eigenvalues, I need to fix the V(G=0) reference, to use the same.
I guess to ways to do that: 1.- Known the alphas values for each pseudopotential and atom, then i can fix the reference by the volume change factor, and with the diference move the eigenvalues to the same reference. But I do not know where the alpha values are in the pseudopotential information. I guess it can calculated by a extrapolation study for an atom in a big cell and the change of vacuum level with the size of the cell... but that is a big work. 2.- Compare the Volume-Eigenvalue product between diferent cell constant, the reference for this magnitude is the "sum alphas", the same value for each cell constant. But in this case I can not know the quantitative change in the eigenvalues. Does anyone know any other way to make this comparison? Do both methods make sense for comparison?
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