Dear Gianluca, > i need U and J for a DMFT (homemade) code. > this is the reason i would prefer to calculate U and J via Wannier > formalism. > Wannier functions i have calculated including d and p states/bands in order > to have more localized states and i can have eigenvalues for self-consistent > unperturbed (alpha=0) and perturbed (alpha finite) runs. > i don`t understand if U and J calculated via derivates of eigenvalues > respect occupancies of this two runs are correct. > what is your opinion?
To calculate U via Wannier formalism one should perturb Wannier states (please take a look on Eq. 26 of http://xxx.lanl.gov/pdf/0801.3500). Usage of Hubbard_alpha perturbes d-states of correlated atom instead. Moreover one needs to subtract the amount of "contrained potential" from Wannier-function energy to compensate the influence of perturbation. The calculation described in http://xxx.lanl.gov/pdf/0801.3500 (The European Physical Journal B 65 1 (2008) 91-98) was performed with modified QE code and I am ready to provide it to you (please, email me directly in that case - there is no any manual, so you will have to ask me questions) Actually, if WF were constructed for p- and d-states there is only slightly difference between d-Wannier and d-atomic states - so you can use traditional QE procedure for U and J calculation. > i have the feeling that i should take care to extrapolate for different > sizes of my system in what i`m doing. It depends on compound under consideration, but in general - yes, you should. Best regards, Dmitry Korotin Ph. D. Student, Institute of Metal Physics S. Kovalevskaya, 18 620041 Ekaterinburg GSP-170 Russia email: dmitry at korotin.name
