hi,
thanks for reply. the assymetry parameter, (Vxx-Vyy)/Vzz, is zero
(wien2k calculation) whereas i got 0.52 from TDPAC (Time dependent
perturbed angular correlation) spectroscopy for a SrTiO3 (STO) defect
structure. EFG component is -1.63 x10^21 V/m2 (wien2k, lapw2 -efg) and i
obtained 1.69
With STO PBE is too covalent. For many properties you need to use either
-eece (my preference), +U or a full hybrid. In addition the default RMT for
Sr in STO is normally too large, something like 2.05 is better.
N.B., be careful not to have the Ti RMT too large as then the tails of the
O 2p
The presence of an EFG and of a non-zero eta is first of all a symmetry
property.
If you get in exp eta=0.5, but in theory eta=0.0 (by symmetry ?), it
simply means that the Hf impurity in PAC is not at the same position or
does not have the same environment than the Hf in your simulations.
In addition to what Peter said:
The small EFG you get is a supercell effect. An isolated Hf-impurity on a
Sr-site (which has a cubic point group, hence zero EFG) would have zero EFG
too. But by using a tetragonal supercell (3x3x2) your break that cubic
symmetry. The tetragonal sublattice of Hf
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