Re: [Wien] EFG + ETA calculation

2015-02-04 Thread Marcelo Barbosa
I tried to make the supercell as cubic as possible, thus the dimensions 1x3x2. It is a slightly distorted near-cubic parallelepiped. I should point that the experiments were done by implanting 111In in the Ga2O3 samples, which decays to 111Cd. This means that the position of the probes is given

Re: [Wien] EFG + ETA calculation

2015-02-04 Thread Peter Blaha
Cd 2+ has a full d shell and thus the contribution of the d-electrons to the EFG should be small. (Try an EFG anylysis). LDA+U can be important for partially filled d-shells (Ti-Ni), but in any case, I'd try GGA+U, but for sure also the other position. PS: Run x nn after relaxations and

Re: [Wien] EFG + ETA calculation

2015-02-04 Thread Peter Blaha
One more thought: How is the time delay for In--Cd decay and EFG measurement by PAC ??? Is the Cd already at a relaxed position or still in the In-position ? You could try to make a structural relaxation for the In-impurity, and then calculate the EFG at Cd in the In position without

Re: [Wien] EFG + ETA calculation

2015-02-03 Thread Peter Blaha
The size should be big enough, at least for a first calculation. Is the supercell nearly cubic, i.e. similar length in all dimensions ? Is there only one Ga site ? How are the distances after relaxation ? Would it correspond to a more or less axial symmetry or is x,y,z very different and

Re: [Wien] EFG + ETA calculation

2015-02-03 Thread Marcelo Barbosa
Dear Prof Blaha, The biggest supercell I used for Ga2O3 was 1x3x2, which has 120 atoms. Then I changed one of the Ga atoms to Cd and relaxed the atomic positions. Since GGA+U or hybrids won’t affect the EFG and ETA in this case, do you think I should try bigger supercells? Thank you very much

Re: [Wien] EFG + ETA calculation

2015-02-02 Thread Peter Blaha
No, I don't think that for this system GGA+U or hybrids are appropriate. Is your supercell large enough (~100 atoms) ?? Did you relax the atomic positions ?? Maybe the Cd sits in a different position ?? Am 02.02.2015 um 20:09 schrieb Marcelo Barbosa: Dear all, I need to calculate the EFG and

[Wien] EFG + ETA calculation

2015-02-02 Thread Marcelo Barbosa
Dear all, I need to calculate the EFG and ETA in a Cd impurity in Ga2O3 but using the usual GGA method gives me an ETA near 1 when experimentally it is known to be between 0.0 and 0.1. I would like then to ask what is the best method to get good EFG and ETA values in such a case: - use GGA+U