[Pw_forum] Non-collinear calculations: magnetic moment relaxation

[Lukashev Pavel]

Dear Gabriele and Andrea,

Thank you very much. I fixed the starting_magnetization and the k-point
sampling. Indeed, it appears that the problem was the insufficient number of
k-points. With K-POINTS AUTOMATIC (4 4 4 1 1 1) I do get magnetic moment
parallel, disregard of their starting orientations.

But now I end up getting another problem. I am trying to impose a constraint
on the magnetization angle (i.e. cosine of angle1, theta) by setting:
constrained_magnetization='atomic direction'
This doesn't seem to work, unless I start with angle1 (theta) being equal
for both iron atoms. When I set them (theta's) different, they do not stay
fixed anymore. I attach my input file along with the portion of the final
output showing the magnetization angles. I thought that probably I have to
constrain the directions separately for each atom, but I did not figure out
how to do it. Simply setting
constrained_magnetization(1)='atomic direction'
constrained_magnetization(2)='atomic direction'
results in error, and I couldn't find in the manual and/or examples any help
on setting these constraints separately.
Any help to resolve this issue is mostly appreciated (i.e. I want to
constrain different magnetization directions on different atoms). I couldn't
find the solution on PW forum archives either.

Gabriele, as for your question, I am using version 4.2. And I include
non-collinear scheme for this somewhat simple system mostly to test how
non-collinearity works with constrained_magnetization, i.e. with fixed
theta. I need this for a bit more complicated project I am currently working
on.

Thank you,

Pavel

Pavel Lukashev, Ph.D.
Research Associate
UNL, Department of Physics & Astronomy
208 Theodore Jorgensen Hall
855 N. 16th Street
Lincoln, NE 68588-0299
Office: (402) 472-2400
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 &control
    calculation='scf'
    restart_mode='from_scratch',
    pseudo_dir = '/home/pavel/QE-4.2/espresso-4.2/pseudo/',
    outdir='/home/pavel/QE-4.2/espresso-4.2/examples/example13/results/TEST/tmp/',
    prefix='fe'
 /
 &system
    ibrav = 1, celldm(1) =5.217, nat= 2, ntyp= 2,
    ecutwfc = 25.0,ecutrho = 200.0,
    report=1,
    occupations='smearing', smearing='mp', degauss=0.02
    noncolin =.true.
    starting_magnetization(1) = 0.5
    starting_magnetization(2) = 0.5
    angle1(1)=90.0
    angle2(1)=0.0
    angle1(2)=0.0
    angle2(2)=0.0
    constrained_magnetization='atomic direction'
    lambda = 1
 /
 &electrons
    conv_thr = 1.0e-8
    mixing_beta = 0.7
 /
ATOMIC_SPECIES
 Fe1 55.847 Fe.pz-nd-rrkjus.UPF
 Fe2 55.847 Fe.pz-nd-rrkjus.UPF
ATOMIC_POSITIONS
 Fe1 0.0 0.0 0.0
 Fe2 0.5 0.5 0.5
K_POINTS AUTOMATIC
4 4 4 1 1 1

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

OUTPUT:
--------------------------------------------------

 ==============================================================================
     atom number    1 relative position :    0.0000   0.0000   0.0000
     charge :     6.406782
     magnetization :          1.989301    0.000000    0.780738
     magnetization/charge:    0.310499    0.000000    0.121861
     polar coord.: r, theta, phi [deg] :     2.137023   68.571554    0.000000
     constrained theta [deg] :    90.000000

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

 ==============================================================================
     atom number    2 relative position :    0.5000   0.5000   0.5000
     charge :     6.406708
     magnetization :          1.737036    0.000000    1.244944
     magnetization/charge:    0.271128    0.000000    0.194319
     polar coord.: r, theta, phi [deg] :     2.137096   54.370619    0.000000
     constrained theta [deg] :     0.000000