Sorry, I don't know, but maybe more details about your calculation would
be needed for someone else to answer your question.
For example, are you doing something similar to the Constraint U
exercise [
http://susi.theochem.tuwien.ac.at/reg_user/textbooks/Constraint_U.pdf ],
which uses the F^0_eff formula of EPL vol. 69, 777 (2005) [
https://doi.org/10.1209/epl/i2004-10416-x ,
https://arxiv.org/abs/cond-mat/0412560v1 (equation 4)]?
For NiO [
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg14460.html
,
http://wien2k-algerien1970.blogspot.com/2016/08/how-to-calculate-u-parameter-in-nickel.html
], I think that gave about:
ε3d_up = 0.119
ε3d_dn = -0.282
If those are the same parameters as in equation 11 of Phys. Rev. B vol.
44, 943 (1991) [ https://doi.org/10.1103/PhysRevB.44.943 ], then it
looks like that would be:
J = ε3d_up - ε3d_dn = 0.12 - (-0.28) = 0.401
Though, one has to keep in mind that the Ueff values obtained from the
Constrained method are known to be of questionable accuracy [
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg15599.html
]. So, the J values might be of questionable accuracy as well. In
addition, well converge results can be needed for such calculations [
https://www.researchgate.net/post/How_to_calculate_U_and_or_J_values_of_DFT_U
].
On 5/12/2018 6:28 AM, Wien2k User wrote:
Dear Prof. Tran and WIEN2k users;
I found in Anisimov's paper the following relation to calculate J
J=E3d'up'(n+0.5,n-0.5)-E3d'dn'(n+0.5,n-0.5)
but I think that the energy of the spin-up electrons is more stable
compared to that of Dn electrons and that's why I found a negative
energy (Do you think that this relationship is reversed?) or my
reasoning is wrong and I have to review my calculations?
Thank you in advance
2018-05-11 18:47 GMT+02:00 Wien2k User <wien2k.u...@gmail.com
<mailto:wien2k.u...@gmail.com>>:
Thank you very much
2018-05-11 16:09 GMT+02:00 Wien2k User <wien2k.u...@gmail.com
<mailto:wien2k.u...@gmail.com>>:
Dear Prof. P. BLAHA and WIEN2k users;
I want to estimate the effective value of Hubbard term "Ueff=U-J"
Can the Hund's Exchange parameter (J) be negative?
Thank you very much.
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