[Pw_forum] Molecular radicals

[Axel Kohlmeyer]

On Sat, 14 Feb 2009, Green Power wrote:

GP> Hi, Can anyone give me an example for molecular radical calculations, for
GP> example,the triplet oxygen molecule? Should I set the multiplicity,

qian,

as always, it would help if you explained a little more
about your background and what exactly you are trying to
achieve and last but not least, which code you are using.
Q-E has two codes, pw.x and cp.x, that can compute single
point energys and MD of molecules.

in pw.x, and i guess that is the result of your confusion,
there are several redundant ways of defining a triplet state.
i'd recommend you use multiplicity=3 and occupations='fixed'.

apart from the fact, that triplet oxygen is a pathological
case, all you need is to do is to set a sufficiently large 
cell and use gamma point only. that'll get you to where a
(more adequate) regular quantum chemistry code would get.

GP> magnetization, band occupation or anything else? I did search the archive,
GP> but I get even more puzzled by the explanations. Probably, an example would
GP> help me understand the problem.

my guess is that you are mostly confused by the different
nomenclatures and requirements that affect people calculating
bulk magnetic materials.

cheers,
   axel.

GP> Thanks.
GP> 
GP> Qian
GP> Clemson University
GP> 

-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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