Dear Tommaso Regarding the metal ions, Matteo Cococcioni already answered your question: you can use the same supercell to calculate both the linear response values. Regarding the O, it is often useful/mandatory to use an on-site correction in transition metal oxides, because if you correct only the metal you may completely miss the p-d coupling. But a reasonable estimate of the U value for O is not very easy. You may be interested in this paper, which investigates the double U(Ti,O) correction in intrinsic and defective TiO2:
Mattioli, et al.; J. Phys. Chem. C 2010, 114, 21694. J. J. Gong pointed out some days ago an alternative method to estimate the ab initio U value in fully occupied (or almost fully occupied) bands, which is often the case of O 2p bands in oxides. It could be interesting to know the opinion of the QE "U-developers" on the possibility to implement the related Hartree-Fock calculation. Anyway the method is discussed here: Mosey, et al.; J. Chem Phys. 2008, 129, 014103 Finally, the implementation of the U+V correction (see Leiria Campo and Cococcioni; J. Phys.: Condens. Matter 2010, 22, 055602), which would be very useful in covalent compounds, should be added to the next QE release. For a comprehensive review, you may also be interested in: Himmetoglu, et al.; Int. J. Quantum Chem. 2014, 114, 14. HTH Giuseppe On Wednesday 28 May 2014 23:10:46 Tommy wrote: > Dear all, > i'm working on a Yttria doped Zirconia, YSZ. I have understood how to > calculate the U values for a single site, but how can i calculate the U > values for both the transition metal inside the same structure, e.g. Zr > and Y in YSZ structure? Do i have to build a supercell even in this case? > Do you think that i need to calculate also the oxygen U contribute? Sorry > for the trivial question, but I'm deeply interested in the method and > understand every feature. Thanks in advance, > Tommaso Francese. > Universit? C? Foscari of Venice. ******************************************************** - Article premier - Les hommes naissent et demeurent libres et ?gaux en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur l'utilit? commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? l'oppression. ******************************************************** Giuseppe Mattioli CNR - ISTITUTO DI STRUTTURA DELLA MATERIA v. Salaria Km 29,300 - C.P. 10 I 00015 - Monterotondo Stazione (RM) Tel + 39 06 90672836 - Fax +39 06 90672316 E-mail: <giuseppe.mattioli at ism.cnr.it> http://www.ism.cnr.it/english/staff/mattiolig ResearcherID: F-6308-2012
