[Pw_forum] ion problem
Nicola Marzari
marzari at MIT.EDU
Wed Nov 14 23:11:44 CET 2007
Rudra Banerjee wrote:
> dear PWSCF users,
> I am new to pwscf and stuck in a question.......is there any way to put
> anion or cation as a unit?the total cluster is charge less but have
> two different types of ion.......can anyone tell me what to do in this
> situation?
> Regards
Dear Rudra,
several have answered this question. Let me add, though, that
standard approximation to the exact exchange-correlation functional
will often fail in "depositing" the right amount of charge on
an ion. This becomes a very relevant failure if you have in the
same unit cell ions of the same type, but of different valence,
e.g. Fe 2+ and Fe 3+ in an oxide, or as ferrous/ferric ions in
solution.
GGA+U formulations help to correct this failure in the solid state
(see e.g. Cococcioni / de Gironcoli, PRB 2005); charge constraints
can also be implemented successfully (see Sit, Cococcioni, Marzari,
PRL 2006, and Van Voorhis PRA 72 024502 (2005)). Other references
are given below.
Best,
nicola
Van Voorhis J. Chem. Theo. Comp. 2 765 (2006); JPCA
110 9212 (2006).
Akai, Blugel, Zeller and Dederichs PRL 1986
Hybertsen, Schluter and Christensen, PRB 1989
Zhang and Satpathy PRB 1991
Ujfalussy, Wang, Nicholson, Shelton, Stocks, Wang and Gyory J. App.
Phys. 1999
Prezhdo, Kindt and Tully JCP 1999
Behler, Delley, Lorenz, Reuter and Scheffler PRL 2005, and
Behler et al PRB 2007
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Prof Nicola Marzari Department of Materials Science and Engineering
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tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu
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