[Pw_forum] input file for isolated atom

[Prasenjit Ghosh]

For Ti atom, the electronic configuration is  [*Ar*].*3d*2.*4s*2. So the
magnetization should be 2.0 Bohr magneton due to the two electrons in the
d-orbital, which is not what you are getting from your calculation.

Also your smearing contribution is -0.00972779 Ry (about 0.1 eV), which I
would say very high. If you would have find the correct magnetic ground
state, then this should have been 0.0 Ry.

As far as the bulk system is concerned, I'm not sure. It depends how Ti bulk
behaves. You can search in the literature to find out what values of degauss
other people have used.

Mixing beta doesn't effect the energy of the system. It just helps you in
convergence.

Prasenjit.

2009/9/11 udayagiri sai babu <udayagiri3 at gmail.com>

> Dear prasenajit this is the part of my output for the posted input file.
> (smearing contribution is there! though it is small ) is the degauss value
> too high for isolated atom or it is high for bulk calculation also? because
> i use around 0.01 Ry value for all my calculations. Does the mixing beta
> value effect the energy of the system?
>
>     one-electron contribution =  -155.91791626 Ry
>      hartree contribution      =    74.49216944 Ry
>      xc contribution           =   -14.37611953 Ry
>      ewald contribution        =   -20.42854186 Ry
>      smearing contrib. (-TS)   =    -0.00972779 Ry
>
>      total magnetization       =     3.24 Bohr mag/cell
>      absolute magnetization    =     3.24 Bohr mag/cell
>
>      convergence has been achieved in  34 iterations
>
>
> On Fri, Sep 11, 2009 at 2:06 PM, Prasenjit Ghosh <prasenjit.jnc at gmail.com>wrote:
>
>> Dear Udayagiri,
>>
>> First of all it's not clear whether you have any question other than
>> whether your input file is correct.
>>
>> Now some comments about your input file:
>>
>> (a) while doing calculations for any zero dimensions you should always set
>> nosym =.true.
>> (b) Your value of degauss is too high.....you should use some value around
>> 0.001 Ry. According to my experience, doing cal. for a single atom is
>> tricky, specially when you are using a smearing. Even that doesn't confirm
>> you will get the correct ground state for the atom. So what you should do is
>> at the end of the calculation check the values of the total magnetization,
>> absolute magnetization and the smearing contribution. The last term should
>> be exactly zero.
>> (c) You don't need to set tstress and tprnfor true.
>> (c) mixing_beta= 0.7 too large.....I would put something smaller....0.3
>> (d) I hope you have checked the convergence of ecut rho & ecutwfc.
>>
>> Prasenjit.
>>
>> 2009/9/11 udayagiri sai babu <udayagiri3 at gmail.com>
>>
>>>  Hi everybody
>>> I want to calculate the cohesive energy of Titanium for that i need to
>>> calculate the energy of an isolated atom previously in the forum somebody
>>> has suggested me to do spin polarisation calculation for the isolated atom.
>>> I have written an input file accordingly some one can see and tell me if my
>>> input script is true. I have read the forum archives on this topic but they
>>> are not exactly answering my question. Can somebody please help me.
>>> *
>>> Input file for isolated atom *
>>>
>>> &control
>>> calculation = 'scf',
>>> restart_mode='from_scratch',
>>> outdir='/home/sai/temp',
>>> prefix='titanium'
>>> pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',
>>> tstress = .TRUE.,
>>> tprnfor = .TRUE.,
>>> /
>>> &system
>>> ibrav=1
>>> celldm(1)=20,
>>> nat=1,
>>> ntyp=1
>>> ecutwfc=25,
>>> ecutrho=250,
>>> occupations='smearing',
>>> smearing='mv',
>>> degauss=0.010000
>>> nspin=2
>>> starting_magnetization(1)=0.2
>>> /
>>> &electrons
>>> conv_thr=1.D-8,
>>> diagonalization='david',
>>> mixing_mode='plain',
>>> mixing_beta= 0.7,
>>> /
>>> ATOMIC_SPECIES
>>> Ti  47.867  Ti.pbe-sp-van_ak.UPF
>>> ATOMIC_POSITIONS (crystal)
>>> Ti     0.00000000    0.00000000    0.00000000
>>> K_POINTS GAMMA
>>>
>>> --
>>> U.Saibabu
>>> PhD student,
>>> Deformation mechanisms modeling group,
>>> Materials engineering department,
>>> IISc Bangalore,
>>> India.
>>>
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://www.democritos.it/mailman/listinfo/pw_forum
>>>
>>>
>>
>>
>> --
>> PRASENJIT GHOSH,
>> POST-DOC,
>> ROOM NO: 265, MAIN BUILDING,
>> CM SECTION, ICTP,
>> STRADA COSTERIA 11,
>> TRIESTE, 34104,
>> ITALY
>> PHONE: +39 040 2240 369 (O)
>>              +39 3807528672 (M)
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
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>>
>>
>
>
> --
> U.Saibabu
> PhD student,
> Deformation mechanisms modeling group,
> Materials engineering department,
> IISc Bangalore,
> India.
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>


-- 
PRASENJIT GHOSH,
POST-DOC,
ROOM NO: 265, MAIN BUILDING,
CM SECTION, ICTP,
STRADA COSTERIA 11,
TRIESTE, 34104,
ITALY
PHONE: +39 040 2240 369 (O)
             +39 3807528672 (M)
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