[Pw_forum] big difference between "total magnetization" and "absolute magnetization" for 4f elements
Stefano de Gironcoli
degironc at sissa.it
Thu Mar 14 10:54:44 CET 2013
dear Kun Tao
the 3D visualization of the up-down charge density in the different
cells you have studied should probably clarify to you what the system is
trying to teach you.
stefano
On 03/13/2013 10:36 PM, 琨陶 wrote:
> I try to force two Gd atom into ferromagnetic with following parameters:
>
> nat= 2, ntyp=2,
> starting_magnetization(1)=1.0,
> starting_magnetization(2)=1.0,
>
> ATOMIC_SPECIES
> Gd1 1.0 Gd.GGA-PBE-paw.UPF
> Gd2 1.0 Gd.GGA-PBE-paw.UPF
> ATOMIC_POSITIONS {crystal}
> Gd1 0.33333333 0.66666667 0.25
> Gd2 0.66666667 0.33333333 0.75
>
> And I got the following results:
>
> total magnetization = 7.55 Bohr mag/cell
> absolute magnetization = 8.02 Bohr mag/cell
>
> In this case, even the "absolute magnetization" is wrong. And the
> magnetic moments on two atoms are 0.47, 7.08, respectively, which are
> are away from the experimental results 7.8 for each atom.
>
> I do not know the reason, perhaps there is a small bug in the code for
> 4f elements or due to some incorrect parameters in my input file. Any
> suggestion is appreciated!
>
> With regards,
> Kun Tao
>
> On 13 March 2013 12:35, mohnish pandey <mohnish.iitk at gmail.com> wrote:
>> Did you try using different initial spin configurations? If your interested
>> in FM ground state then may be you should try initial magnetic configuration
>> as FM. e.g. +1, +1 for both.
>>
>>
>> On Wed, Mar 13, 2013 at 9:03 PM, 琨陶 <taokun76 at gmail.com> wrote:
>>> Thank you for your suggestions. When I set two atoms in the unit cell
>>> to be antiferromagnetic, the "total magnetization" is nearly zero, and
>>> the "absolute magnetization" is about 14.67. And the magnetic moment
>>> for two atoms are about 7.16 and -7.18, which is more or less
>>> acceptable.
>>>
>>> Now, the question is that why "total magnetization" and "absolute
>>> magnetization" differs so much if I want to force two atoms into a
>>> ferromagnetic configuration.
>>>
>>> Any suggestions? Thanks!
>>>
>>> With regards,
>>> Kun Tao
>>>
>>>
>>> On 13 March 2013 11:14, Andrei Malashevich <andrei.malashevich at yale.edu>
>>> wrote:
>>>> If you want to model antiferromagnetic structure, you should define two
>>>> types of atoms, Gd1 and Gd2.
>>>> Change ntyp to 2. Use, e.g.,
>>>> starting_magnetization(1)=1.0
>>>> starting_magnetization(2)=-1.0
>>>>
>>>> ATOMIC_SPECIES
>>>> Gd1 1.0 Gd.GGA-PBE-paw.UPF
>>>> Gd2 1.0 Gd.GGA-PBE-paw.UPF
>>>> ATOMIC_POSITIONS {crystal}
>>>> Gd1 0.33333333 0.66666667 0.25
>>>> Gd2 0.66666667 0.33333333 0.75
>>>>
>>>>
>>>> On Wed, Mar 13, 2013 at 11:05 AM, 琨陶 <taokun76 at gmail.com> wrote:
>>>>> Hi,
>>>>>
>>>>> Yes, the bulk Gd without Hubbard U is antiferromagnetic. If I set the
>>>>> two atoms in the unit cell to be antiferromagnetic, the "total
>>>>> magnetization" should be equal to zero, and the "absolute
>>>>> magnetization" is what I have gotten. Now, however, the "total
>>>>> magnetization" is not zero. Could you give me some suggestions?
>>>>> Thanks!
>>>>>
>>>>> With regards,
>>>>> Kun Tao
>>>>>
>>>>> On 13 March 2013 10:48, Stefano de Gironcoli <degironc at sissa.it> wrote:
>>>>>> are you sure you are defining the correct magnetic structure ?
>>>>>> is Gd maybe antiferromagnetic ?
>>>>>> stefano
>>>>>>
>>>>>> On 03/13/2013 03:19 PM, 琨陶 wrote:
>>>>>>> Dear everyone,
>>>>>>>
>>>>>>> I want to calculate the magnetic properties of bulk Gd whose
>>>>>>> magnetic
>>>>>>> moment is about 8 Bohr magneto/atom. Usually, in the output file
>>>>>>> values of "total magnetization" and "absolute magnetization" should
>>>>>>> be
>>>>>>> nearly the same. However, in my output file, I found a big
>>>>>>> difference
>>>>>>> between them as following:
>>>>>>>
>>>>>>> total magnetization = 8.00 Bohr mag/cell
>>>>>>> absolute magnetization = 15.72 Bohr mag/cell
>>>>>>>
>>>>>>> The good news is that the "absolute magnetization" is close to the
>>>>>>> experimental results (7.86 Bohr mag/atom), the bad news is that the
>>>>>>> "total magnetization" is wrong. Moreover, when I try to calculate
>>>>>>> the
>>>>>>> magnetic moment on each atom with projwfc.x program, I got about 4.1
>>>>>>> Bohr mag/atom.
>>>>>>>
>>>>>>> Could you give me some suggestions? Any advice are appreciated,
>>>>>>> thanks!
>>>>>>>
>>>>>>> Regards,
>>>>>>> Kun Tao
>>>>>>>
>>>>>>>
>>>>>>> Attached below is the input file:
>>>>>>>
>>>>>>> &control
>>>>>>> calculation='scf'
>>>>>>> restart_mode='from_scratch',
>>>>>>> prefix='Gd',
>>>>>>> pseudo_dir = './'
>>>>>>> outdir='./',
>>>>>>> /
>>>>>>> &system
>>>>>>> ibrav= 4, celldm(1)= 6.96, celldm(3)= 1.59,
>>>>>>> nat= 2, ntyp=1,
>>>>>>> nspin = 2,
>>>>>>> starting_magnetization(1)=1.0,
>>>>>>> ecutwfc=55.0,
>>>>>>> ecutrho=220.0,
>>>>>>> occupations ='smearing',
>>>>>>> smearing ='gauss',
>>>>>>> degauss = 0.01,
>>>>>>> /
>>>>>>> &electrons
>>>>>>> diagonalization='david',
>>>>>>> mixing_beta = 0.3,
>>>>>>> conv_thr = 1.0d-8,
>>>>>>> /
>>>>>>> ATOMIC_SPECIES
>>>>>>> Gd 1.0 Gd.GGA-PBE-paw.UPF
>>>>>>> ATOMIC_POSITIONS {crystal}
>>>>>>> Gd 0.33333333 0.66666667 0.25
>>>>>>> Gd 0.66666667 0.33333333 0.75
>>>>>>> K_POINTS {automatic}
>>>>>>> 4 4 4 0 0 0
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>>
>> --
>> Regards,
>> MOHNISH,
>> -----------------------------------------------------------------
>> Mohnish Pandey,
>> PhD Student,
>> Center for Atomic Scale Materials Design,
>> Department of Physics,
>> Technical University of Denmark
>> -----------------------------------------------------------------
>>
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