[Pw_forum] noncolin variable for scalar relativistic pseudopotentials

[Marrazzo Antimo]

Dear Wang,

if you look at the PWscf user guide, how to use the noncolin flag is quite well explained:

“The following input variables are relevant for noncollinear and spin-orbit calculations:

noncolin
lspinorb
starting magnetization (one for each type of atoms)

To make a spin-orbit calculation noncolin must be true. 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 symmetry holds 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 noncollinear spin polarized calculation with spin-orbit interaction. The final spin magnetization might be zero or different from zero depending on the system. Note that the code will look only for symmetries that leave the starting magnetization unchanged.

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 interaction is large. If all the pseudopotentials are scalar relativistic the calculation becomes equivalent to a noncollinear calculation without spin orbit. (Andrea Dal Corso, 2007-07-27) See Example 06 for noncollinear magnetism, Example 07 (and references quoted therein) for spin-orbit interactions.”

If I choose scalar-relativistic pseudopotentials, does this mean nonlinear calculation will be included automatically?

No. Then you must set the noncolin flag to .true. (the default is .false.).

HTH


Antimo Marrazzo
Doctoral Assistant
EPFL STI IMX THEOS
ME-D2 1019 (Bâtiment ME)
Station 9
CH-1015 Lausanne (Switzerland)

Il giorno 04 mar 2016, alle ore 00:01, Mingchao Wang <wmc1406 at gmail.com<mailto:wmc1406 at gmail.com>> ha scritto:

Dear All,

I calculated band structures of hybrid perovskite CH3NH3PbI3. I chose non-relativistic pseudopotentials for H, C, N elements, and scalar-relativistic pseudopotentials for Pb and I elements. In this case, which value of noncolin should I set, noncolin =.false or noncolin =.true?

If I choose scalar-relativistic pseudopotentials, does this mean nonlinear calculation will be included automatically?

Best wishes,

MC
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