[Pw_forum] SOC

[Andrea Dal Corso]

On Mon, 2006-05-15 at 14:54 -0500, Bhagawan Sahu wrote:
> Andrea,
> 
>  In the relativistic PP generation, How the the orbitals, to be pseudozied 
> , are filled in in case of Pt?
> 
> I am trying to generate the Bi PP using the example of Pt given with the 
> distribution.
> 
> for example, in pt.in 
> 
> 7
> 5D  3  2  4.00  0.00  2.10  2.40  1.50
> 5D  3  2  0.00 -0.20  2.10  2.40  1.50
> 5D  3  2  4.00  0.00  2.10  2.40  2.50
> 5D  3  2  0.00 -0.20  2.10  2.40  2.50
> 6P  2  1  0.00 -0.00  3.30  3.30  0.50
> 6P  2  1  0.00 -0.00  3.40  3.40  1.50
> 6S  1  0  2.00  0.00  2.60  2.60  0.50
> 
> 6s is local so is placed at the end.
> 
> four 5d states---> for j=3/2, there are 4 states so max occupation in 
> these states is 4.0 (for up-spin) so down-spin occupation is zero. 
> These counts for first two 5d orbitals (one for up and one for down, 
> j=3/2).

There are not up or down states. The states are eigenfunctions of J^2
and J_z (total angular momentum). They are not eigenfunctions of the
spin operator. When j=3/2, j_z can be -3/2, -1/2, 1/2, -3/2 so there are
four states that can contain a maximum of 4 electrons. The other 4
electrons go in j=5/2 states. 

> 
> for j=5/2 there are 6 states, so maximum occupation in these states is 6.0 
> but we have 4 remaining electrons so next two 5d states are for j=5/2 
> (one up and one down j=5/2).
> 
> What I do not understand is the 6P states. for l=1 we have j=1/2 or 3/2 
> 
> for j=1/2, we have two states with maximum occupation 2.0 
> for j=3/2, we have four states with maxmum occupation 4.0 
> 
> For Bi, there are 3 p-electrons  so 
> the p config is
> 
> 6P  2  1  2.00 -0.00  3.30  3.30  0.50
> 6P  2  1  0.00 -0.00  3.40  3.40  0.50
> 6P  2  1  1.00 -0.00  3.30  3.30  1.50
> 6P  2  1  0.00 -0.00  3.40  3.40  1.50
> 

I think here the configuration is OK. However in US there are two states
for each channel (these are not spin-up and spin-down but two different
energies). Here you set all energies to 0.00 (that means: take the
eigenvalue) and this is not correct. The second energy should be
different from zero:

6P  2  1  2.00 -0.00  3.30  3.30  0.50
6P  2  1  0.00 Energy  3.40  3.40  0.50
6P  2  1  1.00 -0.00  3.30  3.30  1.50
6P  2  1  0.00 Energy  3.40  3.40  1.50

Which energy I do not know. It depends on the atom and is a matter of
cooking. Often an energy slightly higher than the eigenvalue works. In
other cases you need to look at the logarithmic derivative to guess a
reasonable value.


> Is this true?
> 
> the first two are for j=1/2 and last two are for j=3/2
> 
> Also, since pseudotype =3 (ultrasoft), are the entries for rcut(meant for 
> norm conserving PP's) in Pt.in meaningful? I guess they are ignored in the 
> ultrasoft generation.
> 

They are not ignored. The ultrasoft pseudization is done starting from
the norm conserving wavefunctions.


> Sahu
> 
> 
> four 5d states--> why there are four of these?
> 
>  

two values of j and two energies for each j.


> 
> On Thu, 13 Apr 2006, Andrea Dal Corso wrote:
> 
> > Yes the SO term is only in the pseudo-potential but valence states
> > interact with a fully relativistic pseudo-potential at each scf cycle. 
> > We make an approximation because we neglect the spin-orbit coupling
> > outside the core radius where however the effect is expected to be
> > small.
> > 
> > Andrea
> > 
> > 
> > On Wed, 2006-04-12 at 12:43 -0500, Bhagawan Sahu wrote:
> > > Dear pwscf users,
> > > 
> > >   Is it true that
> > > 
> > > the  bulk spin-orbit coupling (SOC) calculation is done using a 
> > > relativistic 
> > > PP for the atom/ion (RRKJ scheme and Andrea Dal Carso's PRB paper) and the 
> > > SOC effect is not included self-consistently on the valence states during 
> > > the scf cycle?
> > > 
> > > Sahu 
> > > 
> > > _______________________________________________
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> > > Pw_forum at pwscf.org
> > > http://www.democritos.it/mailman/listinfo/pw_forum
> > 
> 
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-- 
Andrea Dal Corso                    Tel. 0039-040-3787428
SISSA, Via Beirut 2/4               Fax. 0039-040-3787528
34014 Trieste (Italy)               e-mail: dalcorso at sissa.it