[Pw_forum] [Fwd: paramagnetic structure]

[Subhradip Ghosh]

Dear Davide,

All I wanted to know is the following thing: How does espresso capture the
randomness in local moments in paramagnetic phase?

Subhradip



> Subhradip Ghosh wrote:
>> Dear Davide,
>>
>> Thanks for the reply.
>> I guess I understand that a calculation can be only 'non-spin-pol' or
>> 'spin-pol'(not PM,FM,AFM etc.) . But, don't we use phrases like these
>> during discussions? Atleast, I have been in discussions where people say
>> 'PM calcs or FM calcs' which nobody interprets in the literal sense!
> Dear Subhradip,
>      still I don't understand the difference between a "paramagnetic
> calculation" or a "ferromagnetic calculation". Do you mean that in one
> case the total spin magnetization is zero and in the other case it
> is different from zero?
> Take for instance the oxygen molecule. Would you perform a "paramagnetic"
> calculation or a "ferromagnetic" one? and for bulk iron instead?
>
>> Nevertheless, let me be more specific.
>> How does espresso simulate a paramagnetic state  for a system having
>> unpaired spins ( a system which does not have closed shells).
> Take again the simplest case of the oxygen molecule. We all now that
> the ground state is a triplet (a di-radical). So the calculation will
> be spin-polarized:
>
>    occupations = 'fixed'
>    nspin = 2
>    multiplicity = 3   (multiplicity = 2S+1)
>
> Since there are 12 valence electrons, this will place 7 electrons in
> the spin up channel and 5 electrons in the spin down channel.
>
> Davide
>
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************************************************************************
              Dr. Subhradip Ghosh
              Assistant Professor
              Department of Physics
            Indian Institute of Technology
               Guwahati,Assam-781039
                    India
               E-mail:subhra at iitg.ernet.in
               Phone: +91 361 2582717(O)
                      +91 361 2584717(R)
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