[Pw_forum] radius of integration for local charge and magnetization

[sreekar guddeti]

Respected Sir/Madam,
First of all I would like to thank all the developers of PWSCF for writing
such a beautiful readable code. After following suggestion of Gabriele
Sclauzero, I looked at the .f90 files. I don't have experience in FORTRAN,
but the explanatory comments are really helpful. I have few questions
regarding spin polarized calculations. I would be grateful if you could help
me.
1.make_pointlists.f90 determines the radius of integration for local charge
and magnetization.
    In line 110
                r_m(nt) = 0.5d0*distmin(nt)/1.2d0 * 0.99d0
    integration radius is set to 0.416 of the closest distance from
neighbouring atoms. What is the basis for choosing this factor? I got
confused when the calculation on graphene             ribbon calculation
gives low estimate for the local charge. Here C site contains 4 electrons
and charge corresponding to 0.416* C-C spacing is ~1.710 e. Does this mean
the rest of the charge is diffused in the void?
2. I would like to have the local moments reported after the end of each scf
iteration for unconstrained collinear calculation. I set report = 1 , but it
works only if i set lambda=0, constrained_magnetization='atomic' forcing it
to be a constrained calculation. This workaround doesn't work for
tot_magnetization. I think this has got to do with line 491 of
electrons.f90.
       IF ( noncolin .AND. domag .or. i_cons==1) CALL report_mag()
How should I modify this line so as to report moments for unconstrained
collinear and fixed total_magnetization calculations?
3. The reason I want this is to check the atomic moments and flip one of
them to carry out scf calculation of the ferromagnetic state. The PDOS
calculation also gives a set of moments. Which set of data should be used
for the moments?

PS: I have attached relevant input and output below the signature.

Sincerely,
-- 
Sreekar Guddeti
Undergraduate (5th year)
Engineering Physics
IIT Bombay
India

---------------
Input
---------------
C-C spacing  2.6616 a.u.

---------------
Output  lambda=0.0
---------------
     Generating pointlists ...
     new r_m :   0.2382 (alat units)  1.1084 (a.u.) for type    1
     new r_m :   0.2382 (alat units)  1.1084 (a.u.) for type    2
     new r_m :   0.2382 (alat units)  1.1084 (a.u.) for type    3
     new r_m :   0.2382 (alat units)  1.1084 (a.u.) for type    4
...
...
...

 ==============================================================================
     atom number    1 relative position :    0.0000   0.0000   0.0000
     charge :     1.698873
     magnetization :          0.237509
     magnetization/charge:    0.139804
     constrained moment :     0.400000

 ==============================================================================

 ==============================================================================
     atom number    2 relative position :    0.5000  -0.2887   0.0000
     charge :     1.585202
     magnetization :          0.771066
     magnetization/charge:    0.486415
     constrained moment :     0.800000

 ==============================================================================

 ==============================================================================
     atom number    3 relative position :   -0.5000   0.8660   0.0000
     charge :     1.585089
     magnetization :         -0.710778
     magnetization/charge:   -0.448415
     constrained moment :    -0.700000

 ==============================================================================

 ==============================================================================
     atom number    4 relative position :    0.0000   0.5774   0.0000
     charge :     1.696799
     magnetization :         -0.180967
     magnetization/charge:   -0.106652
     constrained moment :    -0.300000

 ==============================================================================


--------------------------
PDOS calculation
--------------------------
     Atom #   1: total charge =   3.9514, s =  0.9101, p =  3.0413,
                 spin up      =   1.9279, s =  0.4517, p =  1.4762,
                 spin down    =   2.0234, s =  0.4584, p =  1.5651,
                 polarization =  -0.0955, s = -0.0066, p = -0.0889,
     Atom #   2: total charge =   4.1022, s =  0.9810, p =  3.1212,
                 spin up      =   2.1723, s =  0.4962, p =  1.6761,
                 spin down    =   1.9299, s =  0.4848, p =  1.4451,
                 polarization =   0.2424, s =  0.0114, p =  0.2310,
     Atom #   3: total charge =   4.1022, s =  0.9811, p =  3.1211,
                 spin up      =   1.9299, s =  0.4848, p =  1.4451,
                 spin down    =   2.1723, s =  0.4962, p =  1.6761,
------------------------------------------------------------------------------------------
                 polarization =  -0.2424, s = -0.0114, p = -0.2310,   (need
to flip this moment)
------------------------------------------------------------------------------------------
     Atom #   4: total charge =   3.9514, s =  0.9101, p =  3.0412,
                 spin up      =   2.0234, s =  0.4584, p =  1.5651,
                 spin down    =   1.9279, s =  0.4518, p =  1.4762,
                 polarization =   0.0955, s =  0.0066, p =  0.0889,
------------------------
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