charge state of defects

Message

murphy · #1 Post by **murphy** » Sun May 25, 2014 7:13 pm

Dear VASP users,

I would ask two essential questions:

1. I am doing defect calculations in PbSe. If I remove one Pb atom without changing NELECT manually, do I get a vacancy of Pb2+ or neutral Pb? What I want is the formation energy of neutral defects.

2. Why there exist several charge states for defects? For example, we may have Pb defect with charge state ranging from -2 to +2. And people doing defect calculations always include these states. Can't we just calculate the neutral defects?
Your answers are much appreciated.

Best regards,
Murphy

murphy · #2 Post by **murphy** » Sun May 25, 2014 7:16 pm

For my system of a 216-atom PbSe supercell, NELECT is 1080, and for a 215-atom PbSe supercell with one Pb vacancy, NELECT is 1076. And 1074 for a Se vacancy.
<span class='smallblacktext'>[ Edited Sun May 25 2014, 07:24PM ]</span>

zhu · #3 Post by **zhu** » Sun Jun 15, 2014 10:04 am

Hello,

If you remove/add an atom and don't change the NELECT tag, the defect will be neutral. Most time the neutral defects are not always the ground state within a certain range of fermi level, so you need to consider the positive and negative charge states.

zhu