Messages

1

General Questions and Answers / Re: What's the proper spin of Fe2?

« on: September 7, 2009, 05:08 »

Dear zh,
   My Iteration Control Parameters are:

Tolerance  = 0.0001
Criterion  = DensityMatrix
Max. Steps = 100

   I run optimization at 300K and a final static caculation at 0.01 K. The high temperature may lead to fractional occupation of charge of each iron atom.
   Sorry, I don't know where to check the convergence of the magnetic moment of each iron atom. The charge of Fe 0 of the last two iterations are:
 0 Fe     q =  6.00000 [ s:  0.959, s: -0.058, d(-2):  1.028, d(-1):  1.009, d( 0):  1.023, d( 1):  1.009, d( 2):  1.025, d(-2): -0.028, d(-1): -0.041, d( 0): -0.044, d( 1): -0.041, d( 2): -0.025, py:  0.032, pz:  0.120, px:  0.032 ]
 0 Fe     q =  2.00000 [ s:  0.471, s:  0.032, d(-2):  0.000, d(-1):  0.514, d( 0):  0.522, d( 1):  0.514, d( 2):  0.000, d(-2): -0.000, d(-1): -0.059, d( 0): -0.034, d( 1): -0.059, d( 2): -0.000, py:  0.045, pz:  0.008, px:  0.045 ]
 0 Fe     q =  6.00000 [ s:  0.959, s: -0.058, d(-2):  1.028, d(-1):  1.009, d( 0):  1.023, d( 1):  1.009, d( 2):  1.025, d(-2): -0.028, d(-1): -0.041, d( 0): -0.044, d( 1): -0.041, d( 2): -0.025, py:  0.032, pz:  0.120, px:  0.032 ]
 0 Fe     q =  2.00000 [ s:  0.471, s:  0.032, d(-2):  0.000, d(-1):  0.514, d( 0):  0.522, d( 1):  0.514, d( 2):  0.000, d(-2): -0.000, d(-1): -0.059, d( 0): -0.034, d( 1): -0.059, d( 2): -0.000, py:  0.045, pz:  0.008, px:  0.045 ]
    Is charge converged already? And what's the effect of initial_spin =0.9*hbar ? I have tried 0.1*har and 1.0*habar the total net spin are still 8! Is it the proper net spin of Fe2?
    Thank you!

Frsy

    

2

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

3

General Questions and Answers / Re: Is the negative current meaningful?

« on: May 21, 2009, 07:28 »

It's clear. Thank you, Nordland!

4

General Questions and Answers / Re: Is the negative current meaningful?

« on: May 20, 2009, 12:10 »

Dear Nordlan, thank you!
I will do the check! 
BTW: Is the calculated current is related to the two-probe charge "q"? I meant if "q" is not changed when I tuned the parameter will the current be not changed also?

5

General Questions and Answers / Re: Is the negative current meaningful?

« on: May 18, 2009, 11:17 »

Dear Dr. Blom,
    After so long running (including restarting) it converged finally. Thanks for your help. But the convergence is done at high electron temperature (3000 K), do I need restart at the low electron temperature by using initial_calculation=scf?
    Regards,
Frsy

6

General Questions and Answers / Re: Is the negative current meaningful?

« on: May 12, 2009, 10:20 »

Hi Blom! It takes too many steps. Should I wait or do some thing?

# sc  0 : q = 1023.99998 e
# sc  1 : q = 1431.47477 e  Ebs = -1833.10160 Ry  dRho =  1.8823E+00
# sc  2 : q =   58.95118 e  Ebs = -263.23412 Ry  dRho =  5.7266E+00
# sc  3 : q =  974.75854 e  Ebs = -1072.06407 Ry  dRho =  5.6481E+00
# sc  4 : q = 1014.49430 e  Ebs = -1102.57788 Ry  dRho =  3.3595E-01
# sc  5 : q = 1020.13938 e  Ebs = -1114.65361 Ry  dRho =  3.2280E-02
# sc  6 : q = 1028.65257 e  Ebs = -1164.17669 Ry  dRho =  1.1267E-01
# sc  7 : q = 1030.59839 e  Ebs = -1184.38413 Ry  dRho =  5.4742E-02
# sc  8 : q = 1085.91052 e  Ebs = -1221.19005 Ry  dRho =  4.6196E-01
# sc  9 : q = 1046.19352 e  Ebs = -1191.34863 Ry  dRho =  2.5427E-01
# sc 10 : q = 1169.38366 e  Ebs = -1228.02015 Ry  dRho =  7.4900E-01
.....................
# sc 66 : q = 1026.06189 e  Ebs = -1125.28519 Ry  dRho =  2.2362E-02
# sc 67 : q = 1029.73697 e  Ebs = -1161.02460 Ry  dRho =  3.5764E-02
# sc 68 : q = 1030.20989 e  Ebs = -1168.02970 Ry  dRho =  2.4595E-02
# sc 69 : q = 1029.17963 e  Ebs = -1153.29370 Ry  dRho =  1.8653E-02
# sc 70 : q = 1031.50257 e  Ebs = -1181.27999 Ry  dRho =  2.7415E-02
# sc 71 : q = 1030.84315 e  Ebs = -1171.56700 Ry  dRho =  2.0024E-02

7

General Questions and Answers / Re: Is the negative current meaningful?

« on: May 11, 2009, 03:38 »

I run several test, results are:
==================================
1)
    diagonal_mixing_parameter = 0.02,
    circle_points = 30,
    integral_lower_bound = 5*Rydberg,
    temperature = 2300.0*Kelvin

# sc  0 : q = 1023.99998 e
# sc  1 : q = 1424.96286 e  Ebs = -1824.70842 Ry  dRho =  1.8823E+00
# sc  2 : q =   67.28392 e  Ebs = -268.56841 Ry  dRho =  5.8137E+00
# sc  3 : q =  997.65331 e  Ebs = -1080.35030 Ry  dRho =  5.7394E+00
# sc  4 : q = 1024.48027 e  Ebs = -1112.94082 Ry  dRho =  2.7321E-01
# sc  5 : q = 1024.80998 e  Ebs = -1114.54109 Ry  dRho =  1.2772E-02
# sc  6 : q = 1032.20929 e  Ebs = -1154.62139 Ry  dRho =  3.0259E-01
# sc  7 : q = 1033.34392 e  Ebs = -1155.60353 Ry  dRho =  3.7512E-02
# sc  8 : q = 1074.61108 e  Ebs = -1206.45366 Ry  dRho =  3.2210E-01
# sc  9 : q = 1029.26668 e  Ebs = -1133.62307 Ry  dRho =  3.9532E-01
# sc 10 : q = 1024.56511 e  Ebs = -1106.89669 Ry  dRho =  1.3442E-01

2)
    diagonal_mixing_parameter = 0.04,
    circle_points = 10,
    integral_lower_bound = 5*Rydberg,
    temperature = 1300.0*Kelvin

# sc  0 : q = 1023.99998 e
# sc  1 : q = 1416.92054 e  Ebs = -1809.88553 Ry  dRho =  1.8825E+00
# sc  2 : q =   -7.91299 e  Ebs =  219.11140 Ry  dRho =  5.0023E+00
# sc  3 : q =  325.77001 e  Ebs = -722.91447 Ry  dRho =  4.3750E+00
# sc  4 : q = 1014.75194 e  Ebs = -1093.09579 Ry  dRho =  1.6451E+00
# sc  5 : q =  555.21092 e  Ebs = -876.94929 Ry  dRho =  1.5533E+00
# sc  6 : q = 1031.17532 e  Ebs = -1208.11968 Ry  dRho =  1.5766E+00
# sc  7 : q = 1030.46475 e  Ebs = -1194.04483 Ry  dRho =  1.3626E-02
# sc  8 : q =  904.69175 e  Ebs = -1020.76841 Ry  dRho =  7.4575E-01
# sc  9 : q = 1024.13101 e  Ebs = -1119.55928 Ry  dRho =  6.4285E-01
# sc 10 : q = 1032.82502 e  Ebs = -1172.37789 Ry  dRho =  2.3929E-01

3)
    diagonal_mixing_parameter = 0.02,
    circle_points = 10,
    integral_lower_bound = 3*Rydberg,
    temperature = 3300.0*Kelvin

# sc  0 : q = 1023.99998 e
# sc  1 : q = 1431.47477 e  Ebs = -1833.10160 Ry  dRho =  1.8823E+00
# sc  2 : q =   58.95118 e  Ebs = -263.23412 Ry  dRho =  5.7266E+00
# sc  3 : q =  974.75854 e  Ebs = -1072.06407 Ry  dRho =  5.6481E+00
# sc  4 : q = 1014.49430 e  Ebs = -1102.57788 Ry  dRho =  3.3595E-01
# sc  5 : q = 1020.13938 e  Ebs = -1114.65361 Ry  dRho =  3.2280E-02
# sc  6 : q = 1028.65257 e  Ebs = -1164.17669 Ry  dRho =  1.1267E-01
# sc  7 : q = 1030.59839 e  Ebs = -1184.38413 Ry  dRho =  5.4742E-02
# sc  8 : q = 1085.91052 e  Ebs = -1221.19005 Ry  dRho =  4.6196E-01
# sc  9 : q = 1046.19352 e  Ebs = -1191.34863 Ry  dRho =  2.5427E-01
# sc 10 : q = 1169.38366 e  Ebs = -1228.02015 Ry  dRho =  7.4900E-01
# sc 11 : q = 1124.50035 e  Ebs = -1229.82123 Ry  dRho =  3.0367E-01
# sc 12 : q = 1025.19517 e  Ebs = -1127.48006 Ry  dRho =  7.0523E-01
# sc 13 : q = 1022.83390 e  Ebs = -1116.01107 Ry  dRho =  3.1471E-02
========================================================

q is close to original charge but dose not converge. Is this normal? Pelase give me more hints. Thanks!

8

General Questions and Answers / Re: Is the negative current meaningful?

« on: May 8, 2009, 12:02 »

Hi Nordland!
Sure. I wrote a script to generate the bulk.
Acturally, I'm testing integral_lower_bound these days and still have the problem. I have increase the integral_lower_bound to 100 Ry! Do you think it is reasonable? Could you give me more hints?

My input parameters:
two_probe_algorithm_parameters = twoProbeAlgorithmParameters(
    electrode_constraint = ElectrodeConstraints.Off,
    initial_density_type = InitialDensityType.NeutralAtom
)

energy_contour_integral_parameters = energyContourIntegralParameters(
    circle_points = 10,
    integral_lower_bound = 100.0*Rydberg,
    fermi_line_points = 10,
    fermi_function_poles = 4,
    real_axis_infinitesimal = 0.05*electronVolt,
    real_axis_point_density = 0.005*electronVolt
)

I know I should increase circle_points as well but I keep it small to speed-up the test calculation.

9

General Questions and Answers / Re: Is the negative current meaningful?

« on: May 6, 2009, 15:16 »

Thanks for your suggestion. Now I believe it is related to the contour parameter. I will try on these parameters. Thank you again!

10

General Questions and Answers / Re: Is the negative current meaningful?

« on: May 6, 2009, 08:59 »

Could you tell me where is the convergence problem and how to overcome it? All dRho are less than 1E-6. Is this not sufficient?
I guess you mean my current is negatively small so the sign is also negative? It can be treated as zero?
My right electode has higher voltage than the left one. So I suppose the current should flow from right to left.
Thank you!

In your case the current is simply zero and you have a problem with the convergence, however there is not something wrong with a negative current.

In ATK a positive current is a flow of electrons from the left electrode to the right electrode through the scattering region,
an negative current is a flow of electrons from the right electrode to the left electrode.

11

General Questions and Answers / Re: Is the negative current meaningful?

« on: May 6, 2009, 08:32 »

Please take a look on my input files. Thank you!

12

General Questions and Answers / Is the negative current meaningful?

« on: May 6, 2009, 04:33 »

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

13

General Questions and Answers / Re: Confused on optimization

« on: April 23, 2009, 10:05 »

Thank you, Anders and Nordland!

14

General Questions and Answers / Re: Confused on optimization

« on: April 23, 2009, 03:00 »

Manual said "The geometry optimization of a two-probe system is done by mapping the open two-probe system into a periodic atom configuration." "When optimizing the two-probe system, the electrode atoms are always constrained as well as the equivalent atoms"
Someone correct me if I'm wrong please.

15

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