[Pw_forum] how to judge movement of HOMO and LUMO

[Rajdeep Banerjee]

Dear all,
           I want to look at the movement of valence band maxima (VBM /
HOMO) and conduction band minima (CBM/LUMO) of a semiconductor for
different values of applied tensile strain. The problem is how to fix a
reference point to look at such a movement?
1. I can put Fermi energy as reference ... but for a semiconductor it
doesn't mean anything as long as its in the band gap
2. I can put VBM as Fermi level and take that as reference ... but then I
won't see VBM movement
3. I can use mid-point between HOMO and LUMO ... but then both the band
edges will shift by same amount
4. I can fix an arbitrary point in the band gap as reference and check the
movement without any shift ... but I'm a bit sceptical about this chice
though.

           Please advise. Thanks in advance.

warmest regards,
Rajdeep Banerjee
JNCASR
Bangalore, India
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