[Pw_forum] Some questions about non-collinear calculation and penalty function

[Sahar Mirshamsi]

On Thu, 3 Mar 2011, Sahar Mirshamsi wrote:

any idea about answers of these questions?

Sahar


> Hi all,
> I have some questions regarding non-collinear calculation and using
> penalty function in pwscf.
> 1)	In constaint_magnetization ='atomic', is starting magnetization as the
> target magnetization? I have read this post  
> http://www.democritos.it/pipermail/pw_forum/2009-December/015342.html 
> and also in input.f90 I found 
>            mcons(1,nt) = starting_magnetization(nt) * SIN( theta ) * COS(
> phi )
>            mcons(2,nt) = starting_magnetization(nt) * SIN( theta ) * SIN(
> phi )
>            mcons(3,nt) = starting_magnetization(nt) * COS( theta )
>  So it means both magnitude and direction of atomic magnetizations are
> constrained, is this correct?
> 2)	If above statement is correct, then the same problem as posted in above
> link will still exist,  since starting_magnetization=m/n, then for
> constraining the magnitude of magnetization to desired value, we should
> multiply the magnitude of magnetization by charge and then replace it as
> starting_magnitization, is this correct?
> 3)	What is the relation between charge and magnetization printed in scf
> calculation with those which we can get with using projwf.x, I expect they
> should get almost same numbers but in scf output for carbons in Graphene
> nanoribbon I get charge=0.6 and magnetization=0.1 while in projwf.x output
> I get charge=4 and polarization=0.2-0.3 which the latest one makes more
> sense.
> 4)	Also, in some cases of non-collinear calculation with using penalty
> function, when I track "estimated scf accuracy" it is decreasing till
> reaching the threshold  and stopping the job while "total energy" is
> oscillating in some range instead of converging to a number , any idea
> what's the problem?
> 5)	The total energy printed in scf calculation does not include constraint
> energy, right? It's just energy of the structure with the constraint
> configuration of magnetizations, right?
> I appreciate any help in finding the answers of these questions.
> 
> Sahar Mishamsi
> Quantum Theory Project and Physics Department,
> University of Florida
> 
> 
>