[QE-users] Mismatching in Absorption coefficient value

Sudha Priyanka sudhapriyanga24 at gmail.com
Sat Nov 10 09:23:35 CET 2018

Dear Experts

I am calculating optical properties of organic perovskite material by using
quantum espresso 6.1. The calculated optical constants are not exactly
matched with available literatures. Because in my case, the band gap energy
is 3.2 eV but my absorption co-efficient graph shows peaks in the energy
region 1-3 eV too, but maximum absorption occurs in the energy region 8-10
eV. But, If a photon having equal or greater energy than the band gap
energy would be absorbed. Now my question is why the absorption happened
below the band gap energy? Is there any offset value? Should we shift the
default energy values?

Thanks and Regards

Sudha Priyanka

Assistant Professor

Lady Doak College

Madurai, Tamilnadu-625001

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