[QE-users] gradients with charge compensation

[Aleksandra Oranskaia]

Hi dear users and developers of QE,

If one is interested in studying charged state defects -- is it correct to run supercell optimizations with a compensating jellium background ? 
Let’s say, if one is interested in +1 point defect state -- is it correct to add tot_charge = +1 ?

I quickly checked if the gradients for molecular cation optimization are reasonable with such an approach. For this I took small cation with known structure and:
- gaussian09-d.01 optimization with 6-11G**/B3LYP, +1 charge, 1 spin multiplicity gave perfectly matching structure with the real one 
- QE-6.2.1 optimization with vdw-df2/USPP and tot_charge = +1 destroyed the cation, it dissociated; without “jellium” the optimized structure is very close to the real one.

I would greatly appreciate your advice on how to obtain realistic structures of the supercells with charged defects,


Thanks in advance,
Alex.
___
Aleksandra Oranskaia (M.Sc.)
ChemS PhD student, KAUST
Phone: +966 50 1335254







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