[Pw_forum] constrained magnetization calculation to converge at the ferromagnetic state
sreekar guddeti
colonel.sreekar at gmail.com
Thu Aug 25 12:25:30 CEST 2011
Respected Sir/Madam,
1. I would like to perform a constrained magnetization calculation for a
system, whose unconstrained spin polarized calculation gives an
antiferromagnetic state, to converge at the ferromagnetic state.
2. The system is a zigzag graphene nanoribbon(*
http://en.wikipedia.org/wiki/Graphene***) and I would like to flip the
atomic moment at one of the edge site and constrain both the edge site
moments.
3. I calculated the antiferromagnetic edge site moment using PDOS
calculation. I used 'lambda' parameter to constrain the moments.
4.Questions: Is 3) the right way to do it? If yes, what should be value of
lambda? I used lambda =1 and the scf output (given below) is disturbing... I
would like to ask what does "constrained moment : -20.000000" mean and why
is the constrain energy so high. If it is not the right way, I would be
grateful if you could suggest an alternative.
Thanking you,
Yours sincerely,
Sreekar Guddeti
Undergraduate (5th year)
Engineering Physics
IIT Bombay
India
PS: The system namelist for scf calculation and the sample output are given
below and the complete input file is attached.
--------------------------------------
...
==============================================================================
atom number 15 relative position : -3.5000 6.0622 0.0000
charge : 0.983302
magnetization : 0.000256
magnetization/charge: 0.000260
constrained moment : 0.309100
==============================================================================
==============================================================================
atom number 16 relative position : -3.0000 5.7735 0.0000
charge : 1.783674
magnetization : -0.385046
magnetization/charge: -0.215873
constrained moment : -20.000000
==============================================================================
...
...
*constraint energy* (Ryd) = 6095.83663339
---------------------------------
--------------------------------
&SYSTEM
ibrav = 12,
celldm(1) = 4.608737,
celldm(2) = 12.0,
celldm(3) = 10.0,
celldm(4) = -0.50,
nat = 18,
ntyp =10,
starting_magnetization(2)= 0.3091,
starting_magnetization(8)= 0.3091,
occupations='smearing',
smearing='gauss',
degauss=0.01,
nspin=2,
constrained_magnetization='atomic'
lambda = 1
ecutwfc = 50.D0 ,
report = 2
/
--
Sreekar Guddeti
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