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Topics - frsy

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1
General Questions and Answers / What's the proper spin of Fe2?
« on: September 7, 2009, 04:11 »
Dear all,
    I calculated Fe2 cluster with the default basis parameters:

exchange_correlation_type = GGA.PBE
basis_set_parameters = basisSetParameters(
    type = DoubleZetaPolarized,
    radial_sampling_dr = 0.0001*Bohr,
    energy_shift = 0.01*Rydberg,
    delta_rinn = 0.8,
    v0 = 40.0*Rydberg,
    charge = 0.0,
    split_norm = 0.15
)

eigenstate_occupation_parameters = eigenstateOccupationParameters(
    temperature = 0.01*Kelvin
)

electron_density_parameters = electronDensityParameters(
    mesh_cutoff = 150.0*Rydberg,
    initial_spin = 0.9*hbar
)

   ATK gives:
# sc  0 : Fermi Energy =    0.00000 Ry
# sc  1 : Fermi Energy =   -0.15954 Ry  Ebs =   -5.41527 Ry  dRho =  3.0463E-05
   and:
# Total Charge (Spin Up) =   12.00000
# Spin Down
# Total Charge (Spin Down) =    4.00000

   Thus the net spin of Fe2  is 8! But I doubted the high value. I calculated the cluster using VASP (PBE functionals) and got 6! How can I verify which is the proper spin value of Fe2 cluster?
   Thank you!

Frsy

2
Dear all,
    I run two-probe calculation of semi-conduct and got:

#I-V    Bias (Volt)     Current (Ampere)
#I-V    0.0             -0.00e+00
#I-V    0.1             1.08e-21
#I-V    0.2             9.37e-21
#I-V    0.3             -1.84e-17

     The converged charge q of each bias was:
# sc  1 : q =   -0.01908 e  Ebs = -24740.01518 Ry  dRho =  7.0103E-09
# sc  6 : q =   -0.01896 e  Ebs = -24728.50615 Ry  dRho =  3.2187E-07
# sc  6 : q =   -0.01864 e  Ebs = -24696.21142 Ry  dRho =  3.0930E-07
# sc  6 : q =   -0.01822 e  Ebs = -24667.42614 Ry  dRho =  8.5732E-07

      Is the negative current of the bias of 0.3V meaningful? Why the sign is different from 0.1 and 0.2 V?
      Thanks!

Frsy

Parameters used:
    electrode_constraint = ElectrodeConstraints.Off,
    initial_density_type = InitialDensityType.EquivalentBulk
    green_function_infinitesimal = 1.0e-5*electronVolt,
    number_of_points = 100

3
General Questions and Answers / Confused on optimization
« on: April 22, 2009, 12:14 »
Hi all,
What's the difference between two-probe optimization and KohnSham optimization?
From manual I know one built a two-probe geometry and optimized the central region by two-probe method. Can I partially optimize the built two-probe geometry by the KohnSham method directly, then do the static (no optimization) two-probe method calculation on optimized geometry? Are the two ways equal?
I found the calculation of two-probe method costs more than KohnSham method.

Thank you!

Frsy

4
Future Releases / Would NanoLanguage support python 3.x?
« on: April 20, 2009, 11:19 »
We know vnl language is based on python 2.X. Would it upgrade to python 3.0

5
General Questions and Answers / Can atk calculate frequency?
« on: April 14, 2009, 13:24 »
I think atk can't do this directly. Can anyone give some hints? Such as building force constants matrix.
Thanks!

6
Dear all,
    I ran a two-probe job and suffered the power failure. But I have the NetCDF file and the electrode calculation part had been completed. To restart my job I modified the script:

scf = restoreSelfConsistentCalculation(
    filename = 'crash.nc'
)

scf = executeSelfConsistentCalculation(
    self_consistent_calculation=scf,
)

   Then I submitted the job and "top" command showed it was running. But for long time (24hr+) there was no further output after:
# -----------------------------------------------------------------------------
# TwoProbe Algorithm Parameters
# -----------------------------------------------------------------------------
Electrode Constraint = ElectrodeConstraints.Off
Initial Density Type = InitialDensityType.EquivalentBulk

   The "top" command showed it was still running. Did I make something wrong?

Regards,


7
Dear All,
    I run ATK with the command:
      mpirun -np 8 atk job.py &> outfile&
    Then I run "top" to watch the system and eight atk_exec processes were found to be running. But after  the atk output "# sc  0 : Fermi Energy =    0.00000 Ry" in outfile, only three atk_exec processes were running until the end of job. I have changed the parallel number from 8 to 4. There was no change. Only three atk_exec processes were running in the SCF loop.
    Is this normal? My job is a SCF calculation of TwoProbeMethod.
    Regards,

Frsy

8
Dear all,
   The Figure 66 on ATK.TwoProbe manual showed a periodically-repeated heterogeneous two-probe.
(http://quantumwise.com/documents/manuals/ATK-2008.10/ref.twoprobeconfiguration.html#ref.twoprobeconfiguration.notes.repetitions)
   But the lattice lengths on vertical (x/y) direction are same in both electrodes. Is this necessary for calculating heterogeneous two-probe? If it is not,  how the L/R electrodes with different lattices are periodically-repeated on x,y directions? Is there any limitation?
   Regards,

Frsy

9
Dear all,
  I'm new here. Now, I can build and calculate one simple bulk. But how can I optimize the lattice of the bulk while keep the fractional coordinates of all atoms fixed? I looked up the manual and foud ATK ONLY can relax the coordinates of the atom. Do I miss something?
  Regards,

Frsy

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