[Pw_forum] [pw_forum] how to set up spin-orbital coupling calculation in PWscf

[Dal Corso Andrea]

On Thu, 2007-07-26 at 15:50 -0700, Zhiping Yin wrote:
> Dear PWscf users,
> 
> I tried to set up spin-orbital coupling calculation in PWscf without
> spin polarization. I used a full relativistic NCPP and set
> lspinorb=.true.. However, the output is identical with
> lspinorb=.false. I wonder what is the correct way to set up a
> spin-orbital coupling calculation with/without spin polarization. What
> is the requirement with the pseudopotential. Thanks very much. 
> 

The following input variables are relevant for a spin-orbit calculation:

noncolin=.true.
lspinorb=.true.

starting_magnetization

To make a spin-orbit calculation noncolin must be true. If it is false
lspinorb is set to false no matter what you give as input.

If starting_magnetization is set to zero (or not given)  the code makes
a spin orbit calculation without spin magnetization (it assumes that
time reversal is true and it does not calculate the magnetization).
The states are still two component spinors but the total magnetization
is zero.

If starting_magnetization is different from zero it makes a non
collinear spin polarized calculation with spin orbit. The final spin
magnetization might be zero or different from zero depending on the
system.

Furthermore to make a spin-orbit calculation you must use fully
relativistic pseudopotentials at least for the atoms in which you think
that spin orbit is large. If all the pseudopotentials are scalar
relativistic the calculation becomes equivalent to a noncolinear
calculation without spin orbit.

Hope this helps,

Andrea

> Best,
> Zhiping Yin
> 
> -- 
> Zhiping Yin
> graduate student
> department of physics
> UC Davis 
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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