[QE-users] occupation in biological molecules and band gap

[José Xavier]

Dear all,

I'm new in QE. The group that I'm working with usually calculates the properties of biologically relevant molecules, like amino acids, hormones, neurotransmitters, and drugs, and I would like to introduce the QE code to the group. Their previous papers have shown that the bandgap of these crystals is something between 3-5 eV, which I understand to be in the semiconductor range.

I've watched/read some tutorials about QE, and some of these showed that the occupation of semiconductors should be "smearing", other ones that it should be "fixed", but no one showed calculations with this kind of molecules. What value should I use for the SCF and electronic calculations of the crystals that I'm going to work on (amino acids, hormones, neurotransmitters, and drugs)? 

*Are there any differences when the molecule has a metal, like the Heme group?

Besides, I would like to ask if there is a calculation that I could perform to obtain the bandgap of these molecules. Is it only possible if I create the band structure figure and calculate the difference between the peaks in VB and CB?

Thank you for your help,

Sincerely,
José Xavier