QuantumATK Forum
QuantumATK => General Questions and Answers => Topic started by: Old Horse on April 23, 2009, 03:46
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Dear all
I perform a calculation of the transport property of a (4,4) carbon nanotube. I use two (4,4) carbon nanotubetwo as electrodes . The three part of the two probe system form a perfect nanatube. There are 96 C atoms in the scattering region, and there should be 384 valent electrons. However, after the SCF calculation, I found that the electron numbers are 418 and 431 respectively for a constraints and unconstraints calculation (ElectrodeConstraints.Off or ElectrodeConstraints.RealSpaceDensity). Why are there so many electron? is the current I obtained valid then?
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Please post the complete output file, it makes it easier to see exactly where the electrons are (if you used verbosity 10), or at least if there is a substantial difference in the equivalent bulk run compared to the two-probe part.
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I use verbosity_level = 1, following are the out put, a new run with verbosity_level = 10 is just doing and will be post as it finished
# ----------------------------------------------------------------
# Electrodes Calculation
# ----------------------------------------------------------------
# sc 0 : Fermi Energy = 0.00000 Ry
# sc 1 : Fermi Energy = -0.38482 Ry Ebs = -69.59765 Ry dRho = 1.8559E+000 dEbs = -6.9598E+001 Ry dH = 3.7595E-001 Ry
# sc 2 : Fermi Energy = -0.36778 Ry Ebs = -68.21261 Ry dRho = 2.8235E-002 dEbs = 1.3850E+000 Ry dH = 2.7573E-001 Ry
# sc 3 : Fermi Energy = -0.31569 Ry Ebs = -63.98580 Ry dRho = 7.5905E-002 dEbs = 4.2268E+000 Ry dH = 1.0057E-001 Ry
# sc 4 : Fermi Energy = -0.29778 Ry Ebs = -62.50458 Ry dRho = 3.6564E-002 dEbs = 1.4812E+000 Ry dH = 2.1447E-002 Ry
# sc 5 : Fermi Energy = -0.29213 Ry Ebs = -61.93379 Ry dRho = 1.6746E-002 dEbs = 5.7079E-001 Ry dH = 1.2636E-002 Ry
# sc 6 : Fermi Energy = -0.29302 Ry Ebs = -62.00071 Ry dRho = 1.4925E-003 dEbs = -6.6916E-002 Ry dH = 8.7399E-003 Ry
# sc 7 : Fermi Energy = -0.29485 Ry Ebs = -62.09522 Ry dRho = 1.6612E-003 dEbs = -9.4507E-002 Ry dH = 1.8684E-003 Ry
# sc 8 : Fermi Energy = -0.29693 Ry Ebs = -62.20649 Ry dRho = 7.7246E-004 dEbs = -1.1127E-001 Ry dH = 2.9996E-003 Ry
# sc 9 : Fermi Energy = -0.29643 Ry Ebs = -62.16736 Ry dRho = 1.0073E-003 dEbs = 3.9127E-002 Ry dH = 5.8922E-004 Ry
# sc 10 : Fermi Energy = -0.29674 Ry Ebs = -62.18297 Ry dRho = 1.6458E-004 dEbs = -1.5613E-002 Ry dH = 1.1748E-004 Ry
# sc 11 : Fermi Energy = -0.29675 Ry Ebs = -62.18302 Ry dRho = 1.3439E-005 dEbs = -4.5469E-005 Ry dH = 8.7170E-005 Ry
# sc 0 : Fermi Energy = 0.00000 Ry
# sc 1 : Fermi Energy = -0.38086 Ry Ebs = -68.78517 Ry dRho = 1.8392E+000 dEbs = -6.8785E+001 Ry dH = 2.4571E-001 Ry
# sc 2 : Fermi Energy = -0.36384 Ry Ebs = -67.44524 Ry dRho = 1.4385E-002 dEbs = 1.3399E+000 Ry dH = 1.9794E-001 Ry
# sc 3 : Fermi Energy = -0.29667 Ry Ebs = -62.11998 Ry dRho = 6.3980E-002 dEbs = 5.3253E+000 Ry dH = 1.7639E-002 Ry
# sc 4 : Fermi Energy = -0.29652 Ry Ebs = -61.90026 Ry dRho = 1.7505E-002 dEbs = 2.1972E-001 Ry dH = 1.6893E-002 Ry
# sc 5 : Fermi Energy = -0.28661 Ry Ebs = -61.09031 Ry dRho = 1.1313E-002 dEbs = 8.0996E-001 Ry dH = 1.6676E-002 Ry
# sc 6 : Fermi Energy = -0.28950 Ry Ebs = -61.30338 Ry dRho = 2.3269E-003 dEbs = -2.1307E-001 Ry dH = 9.8091E-003 Ry
# sc 7 : Fermi Energy = -0.29288 Ry Ebs = -61.52208 Ry dRho = 1.6173E-003 dEbs = -2.1871E-001 Ry dH = 3.7776E-003 Ry
# sc 8 : Fermi Energy = -0.29457 Ry Ebs = -61.61971 Ry dRho = 5.3327E-004 dEbs = -9.7630E-002 Ry dH = 1.5319E-003 Ry
# sc 9 : Fermi Energy = -0.29444 Ry Ebs = -61.60775 Ry dRho = 2.8972E-004 dEbs = 1.1967E-002 Ry dH = 1.6840E-003 Ry
# sc 10 : Fermi Energy = -0.29514 Ry Ebs = -61.65888 Ry dRho = 5.8815E-004 dEbs = -5.1135E-002 Ry dH = 3.7422E-005 Ry
# sc 11 : Fermi Energy = -0.29515 Ry Ebs = -61.65905 Ry dRho = 9.1541E-006 dEbs = -1.6688E-004 Ry dH = 3.0127E-005 Ry
# ----------------------------------------------------------------
# Equivalent Bulk Calculation (Initial Density for TwoProbe)
# ----------------------------------------------------------------
# sc 0 : Fermi Energy = 0.00000 Ry
# sc 1 : Fermi Energy = -0.38074 Ry Ebs = -552.56692 Ry dRho = 1.8729E+000 dEbs = -5.5257E+002 Ry dH = 3.6268E-001 Ry
# sc 2 : Fermi Energy = -0.37559 Ry Ebs = -549.31003 Ry dRho = 7.0420E-003 dEbs = 3.2569E+000 Ry dH = 3.3537E-001 Ry
# sc 3 : Fermi Energy = -0.29756 Ry Ebs = -499.99741 Ry dRho = 1.1402E-001 dEbs = 4.9313E+001 Ry dH = 8.5807E-002 Ry
# sc 4 : Fermi Energy = -0.30158 Ry Ebs = -501.94452 Ry dRho = 1.7386E-002 dEbs = -1.9471E+000 Ry dH = 4.6462E-002 Ry
# sc 5 : Fermi Energy = -0.27933 Ry Ebs = -487.57936 Ry dRho = 3.2493E-002 dEbs = 1.4365E+001 Ry dH = 6.5018E-002 Ry
# sc 6 : Fermi Energy = -0.28388 Ry Ebs = -489.84275 Ry dRho = 1.0773E-002 dEbs = -2.2634E+000 Ry dH = 2.8395E-002 Ry
# sc 7 : Fermi Energy = -0.28664 Ry Ebs = -491.15145 Ry dRho = 2.6061E-003 dEbs = -1.3087E+000 Ry dH = 1.2352E-002 Ry
# sc 8 : Fermi Energy = -0.28778 Ry Ebs = -491.84633 Ry dRho = 1.3781E-003 dEbs = -6.9488E-001 Ry dH = 1.0109E-002 Ry
# sc 9 : Fermi Energy = -0.29124 Ry Ebs = -493.73057 Ry dRho = 2.3066E-003 dEbs = -1.8842E+000 Ry dH = 2.8443E-003 Ry
# sc 10 : Fermi Energy = -0.29230 Ry Ebs = -494.31810 Ry dRho = 8.9495E-004 dEbs = -5.8753E-001 Ry dH = 1.7153E-003 Ry
# sc 11 : Fermi Energy = -0.29278 Ry Ebs = -494.41671 Ry dRho = 8.0515E-004 dEbs = -9.8605E-002 Ry dH = 1.0004E-003 Ry
# sc 12 : Fermi Energy = -0.29289 Ry Ebs = -494.45677 Ry dRho = 9.6865E-005 dEbs = -4.0060E-002 Ry dH = 9.4689E-004 Ry
# sc 13 : Fermi Energy = -0.29329 Ry Ebs = -494.60205 Ry dRho = 2.1890E-004 dEbs = -1.4528E-001 Ry dH = 4.1363E-004 Ry
# sc 14 : Fermi Energy = -0.29329 Ry Ebs = -494.59644 Ry dRho = 7.2030E-005 dEbs = 5.6127E-003 Ry dH = 1.6898E-004 Ry
# sc 15 : Fermi Energy = -0.29330 Ry Ebs = -494.59801 Ry dRho = 2.7905E-005 dEbs = -1.5687E-003 Ry dH = 1.4534E-004 Ry
# ----------------------------------------------------------------
# TwoProbe Calculation
# ----------------------------------------------------------------
# sc 0 : q = 383.99017 e
# sc 1 : q = 412.97473 e Ebs = -354.49262 Ry dRho = 1.3014E+002 dEbs = -3.5449E+002 Ry dH = 5.6512E-001 Ry
# sc 2 : q = 414.47407 e Ebs = -360.82747 Ry dRho = 4.1782E+000 dEbs = -6.3349E+000 Ry dH = 3.6826E-001 Ry
# sc 3 : q = 416.83350 e Ebs = -370.41142 Ry dRho = 5.0302E+000 dEbs = -9.5839E+000 Ry dH = 1.3006E-001 Ry
# sc 4 : q = 417.42461 e Ebs = -371.43589 Ry dRho = 2.6024E+000 dEbs = -1.0245E+000 Ry dH = 7.9374E-002 Ry
# sc 5 : q = 418.13382 e Ebs = -373.14609 Ry dRho = 2.3687E+000 dEbs = -1.7102E+000 Ry dH = 6.2686E-002 Ry
# sc 6 : q = 417.93744 e Ebs = -372.48404 Ry dRho = 7.5953E-001 dEbs = 6.6205E-001 Ry dH = 5.4537E-002 Ry
# sc 7 : q = 418.99944 e Ebs = -376.07679 Ry dRho = 2.8583E+000 dEbs = -3.5928E+000 Ry dH = 9.5793E-002 Ry
# sc 8 : q = 418.10739 e Ebs = -372.70887 Ry dRho = 1.8139E+000 dEbs = 3.3679E+000 Ry dH = 5.3472E-002 Ry
# sc 9 : q = 418.49108 e Ebs = -374.21267 Ry dRho = 9.1968E-001 dEbs = -1.5038E+000 Ry dH = 9.8387E-003 Ry
# sc 10 : q = 418.44168 e Ebs = -374.00448 Ry dRho = 9.6490E-002 dEbs = 2.0819E-001 Ry dH = 4.2329E-003 Ry
# sc 11 : q = 418.46548 e Ebs = -374.14441 Ry dRho = 1.0174E-001 dEbs = -1.3993E-001 Ry dH = 2.2833E-003 Ry
# sc 12 : q = 418.45230 e Ebs = -374.10146 Ry dRho = 2.5784E-002 dEbs = 4.2953E-002 Ry dH = 6.8800E-004 Ry
# sc 13 : q = 418.45086 e Ebs = -374.10787 Ry dRho = 7.3693E-003 dEbs = -6.4170E-003 Ry dH = 5.3064E-004 Ry
# sc 14 : q = 418.45132 e Ebs = -374.11474 Ry dRho = 5.7638E-003 dEbs = -6.8673E-003 Ry dH = 4.6244E-004 Ry
# sc 15 : q = 418.45306 e Ebs = -374.13005 Ry dRho = 1.7255E-002 dEbs = -1.5309E-002 Ry dH = 2.9308E-004 Ry
# sc 16 : q = 418.45328 e Ebs = -374.13256 Ry dRho = 2.2903E-003 dEbs = -2.5129E-003 Ry dH = 2.6709E-004 Ry
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Although I haven't seen the geometry, my guess is that the electrode is too short. If it's only 1 period, or even 2, this is too short and will, even if the calculation converges (which is sometimes hard, when the electrodes are too short), lead to the wrong results.
It was observant of you to note the charges, but you would probably have seen it very clearly in the transmission spectrum later. This is an ideal system, but I would not be surprised if the transmission spectrum comes out less than perfect (not integer plateaus).
So, increase the electrodes (use 4 periods) and let's see what happens!
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yes, just as you say, I use only one period. Now I reset it to 4 period and and see what happen!
thanks