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Messages - alan

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1
In dft the columb interaction is included in a mean field approximation. With the +U correction you can simulate local correlation effects.
For brief introduction I suggest you read the chapter about DFT in the ATK manual, there you can also found references to other texts.
Thank you very much, sir. I have read the relevent chapter you suggested, but it is still unclear for me, could you give me any other informations about that? Thank you for your help and reply.

2
Hello,everyone,

The physics origin of magnetism is the Coulomb interaction, if it does not take the Coulomb interaction into account, how can we valid the calculated results?

So in the ATK calculation, is it necessary to consider the coulomb interaction? And how induce the coulomb interaction in the DFT calculations?

What is the effect on magnetism when we consider the Coulomb interaction explicitly?

And could anybody provide me some references about the effects?

Thank you,these questions have puzzled me a long time, please help me.

3
I have the similar questions:

In the ATK calculation, is it necessary to consider the coulomb interaction? And how induce the coulomb interaction in the DFT calculations?

What is the effect on magnetism when we consider the Coulomb interaction explicitly?

And could anybody provide me some references about the effects?

4
Dear zh and Anders Blom,

i have made 2 repetitions of the electrodes and   increased the surface layers.
the script works well in spin-polarized calucation now.

Thank you very much.

5
thanks for your replies.
i have increase one repetition to the left (or right) electrode surface layer.
but I still get the error:
# ----------------------------------------------------------------
# TwoProbe Calculation
# ----------------------------------------------------------------
# sc  0 : q =  207.88044 e
# sc  1 : q =  221.07823 e  dRho =  3.5942E+01
Traceback (most recent call last):
  File "88cbn.py", line 312, in ?
    runtime_parameters = runtime_parameters
ATKError: inverse(DZMatrix const &) : Could not LU factorize!
I also attempt to use the   " initial_density_type = InitialDensityType.NeutralAtom"and LDA,the problem can't be solved.
everytime,to do the "TwoProbe Calculation",the error comes out.
what can i do ?

6
Hi,
i have a script 8.py for the two probe configuration.
when i drop the script to the Result Browser, two configuration 8.png looks well. when you drag the script into Atomic Manipulator first and then drag into either Result Browser or Nanolanguage Scripter,yuo will see thetwo configuration is wrong 81.png. i find the issue is on the equivalent_atoms.
the script is correct or not?
moreover, i have the same problem when i run the script 8cbn.py:
# TwoProbe Calculation
# ----------------------------------------------------------------
# sc  0 : q =  172.73989 e
Traceback (most recent call last):
  File "<string>", line 299, in ?
ATKError: inverse(DZMatrix const &) : Could not LU factorize!\
what can i do?

7
Thanks for your reply.
another question: how to find their most stable magnetic states( ferromagnetic, antiferromagnetic, non-magnetic, or other states)?
to test and  find their most stable magnetic states.can we just by setting the different value (0.0,1.0,-1.0 or a random number among -1,1) as the initial_scaled_spin.and Comparing their total energy,chose the configuration with lowest energy?Is that OK? or we shold have other calculations?

8
Hi

I am confused with setting the value of the "initial_scaled_spin" for the spin-polarized calculation.
Does the different value for the initial_scaled_spin will effect the last  result ,such as the DOS or transmission?Is there any difference with the calculation between  the initial_scaled_spin =0 and 1(-1) for the reslut,besides the speed of  computing.
what is the reasonable understanding of the initial_scaled_spin in our calculation? which physical quantity should we caluate or analyse before?
If for the unhomogeneoustwo-probe system, can we set the uniform value for different atoms? is that correct? if we can not ,what is the Process for we get the initial_scaled_spin?
In a word, i want to know how can set the correct and reasonable value for initial_scaled_spin for any system.

Need your help

10
Hi,
  I want to calculate the spin dependent Projected Density of States.how can i modify the script of the Density Of States:
f = open('pdos.dat','w') 
import numpy
projecte_density_of_states = calculateProjectedDensityOfStates(
    self_consistent_calculation = scf,
    projection_atoms =[11,18],
    energies = numpy.arange(-1.0, 1.0+0.1, 0.01)*electronVolt,
    brillouin_zone_integration_parameters = brillouinZoneIntegrationParameters((1, 1)),
    green_function_infinitesimal = 1.0e-5*electronVolt
)

energies = projecte_density_of_states.energies()
pdos = projecte_density_of_states.projectedensityofstates()
if len(pdos.shape)==2:
    # spin-polarized
    print '                    Projected Density of states'
    print 'Energy (eV)     Spin-up       Spin-down'
    print '------------------------------------------'
    for i in range(len(energies)):
        print "%g\t%g\t%g\n" % ( energies.inUnitsOf(eV),
            pdos[0,i].inUnitsOf(eV**(-1)),pdos[1,i].inUnitsOf(eV**(-1)) )
        s = '%g\t%g\t%g\n' % ( energies.inUnitsOf(eV),
            pdos[0,i].inUnitsOf(eV**(-1)),pdos[1,i] .inUnitsOf(eV**(-1)))
        f.write(s)
else:
    print 'Energy (eV)    Projected Density of states'
    print '-----------------------------------'
    for i in range(len(energies)):
        print "%g\t%g\n" % ( energies.inUnitsOf(eV**(-1)),pdos )
        s = '%g\t%g\n' % ( energies.inUnitsOf(eV**(-1)),pdos )
        f.write(s)
f.close()
i have replaced the Density Of States with Projected Density of States.but it does not worked.i want to know how can i deal with the red part i indicated in the script above.

11
 Hi,
i have got the MullikenPopulation,
 -----------------------------------------------------------------------------
# Mulliken Population
# -----------------------------------------------------------------------------
# Index      Population (Up,Down)
    c       0   (  1.8061 ,  2.0663 )
    c       1   (  2.0075 ,  1.9499 )
    c       2   (  1.9609 ,  2.0365 )
    c       3   (  2.0253 ,  1.9804 )
    c       4   (  1.9804 ,  2.0253 )
    c       5   (  2.0365 ,  1.9609 )
    c       6   (  1.9499 ,  2.0075 )
    c       7   (  2.0663 ,  1.8061 )
    H       8   (  0.5873 ,  0.5797 )
    H       9   (  0.5797 ,  0.5873 )
how can i get the magnetic moment of each atoms ,the system is the unit cell of zigzig carbon nanoribbon.
Thanks.

12
actually´╝î i know a little about  ferromagnetic, anti-ferromagnetic, or ferrimagnetic states ,but i am not sure about the  magnetism properties of graphene ribbon. i want to know if i want to get an  ferromagnetic system.the initial_scaled_spin = [ 1., 1., 0., 0., 0., 0., -1., -1., 0., 0. ] the orinitial_scaled_spin = [ 1., -1., 0., 0., 0., 0., 1., -1., 0., 0. ].and initial_scaled_spin = [ 1., 0., 0., 0., 0., 0., 0., -1., 0., 0. ]which one is ture?or both ok ? i read some correlative papers,but i can get the conclusion for the settings in atk calculation.

13
hi everyone,
    i mean if we want to calculate the spin depended properties.so we should give an initial spin to the structure.i am confused with the  value of " initial_scaled_spin" .just like the tutorial show the graphene ribbon initial_scaled_spin = [ 1., 1., 0., 0., 0., 0., -1., -1., 0., 0. ].i do not know why he setlike this.and if i set the value as initial_scaled_spin = [ 1., 0., 0., 0., 0., 0., 0., -1., 0., 0. ]orinitial_scaled_spin = [ 1., -1., 0., 0., 0., 0., 1., -1., 0., 0. ].is that ok? i want to know what does the initial_scaled_spin mean.
thank for your help.

14
General Questions and Answers / Re: why?
« on: June 6, 2009, 11:46 »
I have sent the files to you by e-mail.

15
General Questions and Answers / Re: why?
« on: June 6, 2009, 10:38 »
I am sorry ,i came agian.
1.Calculate the transmission spectrum or a band structure for the polarized system, find an energy where the transmission is different from zero, or an energy where there is some bands.the  local density of states for this energy is fig.1(spin up)and fig 2(spin down). I found that is seems like centrosymmetric.it is not perfect periodical.what does it mean( have i  done an wrong calculate)?
2.For the unpolarized system, there does not exit the enery at which the transmission is 0.so it  is still not been worked out now.

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