Hello, I calculated the band structure of bulk amorphous silicon (64 atoms tetrahedrically coordinated). I found an HOMO-LUMO band gap of about 0.7 eV. Then I performed the OpticalCalculation, but I have that the resulting imaginary dielectric function has a peak at E<0.7. How is this possible? I expect that each valence-to-conduction transition must be larger than the bang-gap!
Roberto
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