[Pw_forum] big difference between "total magnetization" and "absolute magnetization" for 4f elements
琨陶
taokun76 at gmail.com
Thu Mar 14 15:04:02 CET 2013
Dear Stefano,
Could you give me some suggestions about how to visualization of the
up-down charge density?
With regards,
Kun Tao
On 14 March 2013 05:54, Stefano de Gironcoli <degironc at sissa.it> wrote:
> 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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