Messages

1

General Questions and Answers / Re: Can I use SGGA+U Exchange-correlation potential for transport calculation?

« on: December 3, 2011, 08:01 »

What is fundamental reason why you apply the U on the 2s orbital of O?  The LDA+U method may be  suitable for the transition metal oxides with strongly correlations such as NiO, FeO, and so on, but it may be not suitable for the MgO. 

Sorry, I applied the U on the Mg 3s orbital, I made a slip of the pen. What I did is followed the Tutorial "Bandgap of MgO with LDA+U: Tutorial how to fit LDA+U to an experimental band gap", published online by QuantumWise, but i can't find it now.

2

General Questions and Answers / Re: Can I use SGGA+U Exchange-correlation potential for transport calculation?

« on: December 2, 2011, 05:44 »

I used the latest version atk-11.8.1 with a trial license, I have checked the band structure of MgO carefully, I found I can get correct band gap of 7.7 eV for MgO when I applied 23 eV of U value to the Mg DZP 3s orbitals(including split and polarization orbitals), which is different from the Tutorial "Bandgap of MgO with LDA+U", where need only about 10 eV can get correct band gap. If I use the value of 10 eV , I only get the band gap about 6.4 eV.

My doubt is it is reliable using SGGA+U Exchange-correlation potential for transport calculation?  e.g. for fe/mgo/fe mtj. because the correct band gap is important for device simulating. It seems validity for bulk calculation.

thanks!

3

General Questions and Answers / Re: Can I use SGGA+U Exchange-correlation potential for transport calculation?

« on: November 30, 2011, 16:23 »

I added the U value of 23 eV to the Mg 3s shell, so I can get the band gap of MgO about 7.7eV

4

General Questions and Answers / Can I use SGGA+U Exchange-correlation potential for transport calculation?

« on: November 30, 2011, 08:36 »

I calculated transmission spectrum of fe/mgo/fe magnetic tunnel junction using the SGGA+U Exchange-correlation potential for Mg, but the result seems wrong:

 energy (eV)      T(up)         T(down)
 -2.000000e+00   7.359234e-02   1.575396e-02
 -1.900000e+00   4.752671e-02   3.328986e-02
 -1.800000e+00   3.876577e-02   3.769258e-02
 -1.700000e+00   5.075683e-02   7.200586e-02
 -1.600000e+00   4.783458e-02   7.238770e-02
 -1.500000e+00   6.749334e-02   8.836559e-02
 -1.400000e+00   1.207360e-01   1.279868e-01
 -1.300000e+00   1.755151e-01   1.565134e-01
 -1.200000e+00   2.025906e-01   1.246247e-01
 -1.100000e+00   2.976305e-01   1.338918e-01
 -1.000000e+00   2.001293e-01   1.287574e-01
 -9.000000e-01   2.268985e-01   1.274554e-01
 -8.000000e-01   1.548494e-01   7.139636e-02
 -7.000000e-01   1.446821e-01   1.005546e-01
 -6.000000e-01   1.072199e-01   5.061934e-02
 -5.000000e-01   8.161175e-02   4.926054e-02
 -4.000000e-01   7.442812e-02   1.562091e-02
 -3.000000e-01   6.174792e-02   8.025265e-03
 -2.000000e-01   3.476308e-02   2.165560e-03
 -1.000000e-01   3.328062e-02   2.250245e-03
  0.000000e+00   1.576522e-02   1.952985e-03
  1.000000e-01   2.109151e-02   3.575160e-04
  2.000000e-01   7.334028e-03   8.772420e-04
  3.000000e-01   4.601747e-03   8.120860e-06
  4.000000e-01   1.030548e-02   1.016774e-05
  5.000000e-01   1.381889e-02   3.465895e-05
  6.000000e-01   8.526817e-03   9.408154e-05
  7.000000e-01   1.546726e-03   6.761147e-08
  8.000000e-01   1.867503e-04   1.264305e-08
  9.000000e-01   4.622378e-05   3.432443e-09
  1.000000e+00   1.525821e-05   1.059971e-09
  1.100000e+00   5.868977e-06   3.507419e-10
  1.200000e+00   2.477182e-06   1.242672e-10
  1.300000e+00   1.109999e-06   5.010421e-11
  1.400000e+00   5.169824e-07   2.574732e-11
  1.500000e+00   2.465086e-07   1.854089e-11
  1.600000e+00   1.189180e-07   1.671491e-10
  1.700000e+00   5.748862e-08   3.517107e-11
  1.800000e+00   2.766303e-08   8.078225e-10
  1.900000e+00   1.323612e-08   6.729046e-09
  2.000000e+00   6.379466e-09   2.075338e-08

and the calculated transmission spectrum without hubbard u is:

energy  ( eV)     T(up)         T(down)
 -2.000000e+00   2.192314e-13   2.699950e-11
 -1.900000e+00   1.159918e-13   2.312347e-10
 -1.800000e+00   1.909143e-13   4.977940e-11
 -1.700000e+00   6.634284e-14   4.964251e-11
 -1.600000e+00   8.036492e-14   2.968821e-11
 -1.500000e+00   4.031784e-13   1.144877e-11
 -1.400000e+00   1.754009e-12   5.143252e-09
 -1.300000e+00   1.335622e-10   6.444458e-12
 -1.200000e+00   1.250935e-07   7.796190e-12
 -1.100000e+00   3.064643e-09   8.962319e-12
 -1.000000e+00   4.067027e-09   9.051339e-12
 -9.000000e-01   7.235466e-09   9.229104e-12
 -8.000000e-01   1.032260e-08   1.355638e-11
 -7.000000e-01   1.056395e-08   7.930413e-12
 -6.000000e-01   1.125172e-08   7.050996e-12
 -5.000000e-01   1.320135e-08   1.051105e-11
 -4.000000e-01   1.669488e-08   9.097804e-12
 -3.000000e-01   2.235478e-08   1.680387e-12
 -2.000000e-01   3.144456e-08   1.079387e-12
 -1.000000e-01   4.618436e-08   1.181674e-12
  0.000000e+00   7.052900e-08   3.071133e-12
  1.000000e-01   1.119533e-07   1.215069e-11
  2.000000e-01   1.835724e-07   6.310866e-11
  3.000000e-01   3.138680e-07   3.397042e-10
  4.000000e-01   5.625070e-07   1.690368e-09
  5.000000e-01   1.067489e-06   7.922923e-09
  6.000000e-01   2.176246e-06   3.772807e-08
  7.000000e-01   4.871430e-06   2.208804e-07
  8.000000e-01   1.241580e-05   2.541869e-06
  9.000000e-01   3.863144e-05   1.034904e-03
  1.000000e+00   1.739469e-04   6.224177e-03
  1.100000e+00   1.886715e-03   5.034524e-03
  1.200000e+00   6.564475e-03   3.269805e-03
  1.300000e+00   8.198202e-03   2.480162e-03
  1.400000e+00   9.490935e-03   3.637451e-03
  1.500000e+00   1.284054e-02   3.401341e-03
  1.600000e+00   1.978573e-02   3.150266e-03
  1.700000e+00   2.558336e-02   2.134390e-03
  1.800000e+00   2.911208e-02   4.348823e-03
  1.900000e+00   3.081802e-02   7.713965e-03
  2.000000e+00   3.414162e-02   1.059903e-02

Is it reliable using SGGA+U Exchange-correlation potential for transport calculation?

5

General Questions and Answers / Re: Does the current calculation make sense if a valence band enter the bias window?

« on: May 9, 2011, 20:46 »

I  think in bulk material the valence electrons don't participate conduction, but in a tunnel junction, they can participate in tunnel process, so my previous thought is wrong

6

General Questions and Answers / Does the current calculation make sense if a valence band enter the bias window?

« on: May 9, 2011, 11:29 »

Hi, everyone!
I don't make very clear about this point, the valence electrons should not participate the conducting, but the transmission calculation in ATK includes all states in the energy range in spite of it's a valence state or a conduction band, my question is does the current calculation make sense if a valence band enter the bias window?

7

General Questions and Answers / Re: error when calculate scf of LaMnO3

« on: October 16, 2010, 01:54 »

I change the parameter green_function_infinitesimal in function calculateTransmissionCoefficients() from default to 1.0e-10ev then the two values are equal. So I think this difference maybe comes from numerical error.

8

General Questions and Answers / Re: error when calculate scf of LaMnO3

« on: October 14, 2010, 22:53 »

I have calculated transmission coefficients and transmission eigenvalues for a two-probe system, I found transmission coefficient and the sum of transmission eigenvalues are not equal at (0.0, 0.0) k-point, one is 8.59771e-11 and the other is 2.10421766e-13. I then calculated the two values at other k-points, some k-points they are equal and some are not,but the difference is small.
Why they are different?

9

General Questions and Answers / Re: error when calculate scf of LaMnO3

« on: October 14, 2010, 18:40 »

Additional comment:
LaMnO3 is one of typical materials with strongly correlated effect. The LDA/GGA may not properly describe the ground states of this compound. The methods beyond LDA/GGA are needed.

Thanks for your comment. I just want to inspect the band structure of it ,because it is the parent of many other manganates

10

General Questions and Answers / Re: error when calculate scf of LaMnO3

« on: October 14, 2010, 18:10 »

The reason we cannot support it is rather technical, and not really related to ATK (believe it or not...).

There is a workaround, however. Using the two attached scripts you can actually calculate a normal La bulk crystal with ATK 10.8. I trust you can read Python enough to understand how to modify them to run your crystal instead. It will require some copying and pasting

Thank you very much! It worked

11

General Questions and Answers / Re: error when calculate scf of LaMnO3

« on: October 12, 2010, 13:59 »

thanks for reply ,I come back to atk 2008.10 as well, but I can't calculate PDOS for bulk

12

General Questions and Answers / error when calculate scf of LaMnO3

« on: October 11, 2010, 21:05 »

when I make a scf calulation of LaMnO3 using the newest version of atk 10.8.2 , the error occured:
"GGABasis.Lanthanum_SingleZeta,
AttributeError: 'module' object has no attribute 'Lanthanum_SingleZeta'
NanoLanguageScript execution failure"
can anyone help me?