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General Questions and Answers / Re: the average Hartree difference potential under an external electric field
« on: October 30, 2019, 03:56 »
Thank you so much for your help!
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General Questions and Answers / Re: the average Hartree difference potential under an external electric field
« on: October 28, 2019, 07:17 »
Now, by setting the right boundary condition to DirichletBoundaryCondition(vacuum + shift), the following Hartree differential potential can be obtained. Here, the vacuum is the projection of the average Hartree differential potential (about 4.4 eV) along the c-axis, and the shift is ±10 eV. the voltages of left and right electrode were set to 0 V.
My question is, is the strength of the electric field set by the shift here? If so, does the shift = 10 eV meaning that a 10 V electric field is applied to the surface? What is the relationship between the electrode voltage and the electric field?
My question is, is the strength of the electric field set by the shift here? If so, does the shift = 10 eV meaning that a 10 V electric field is applied to the surface? What is the relationship between the electrode voltage and the electric field?
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General Questions and Answers / Re: the average Hartree difference potential under an external electric field
« on: October 25, 2019, 10:33 »
Thank you so much for your help. But, why HartreeDifferencePotential at (Left=1.0, Right=0.0 V) is same as it at (Left=0.0, Right=1.0 V). Is the (Left=1.0, Right=0.0) meaning a positive field?
PS, I used QuantumATK 2018.06-SP1-1.
PS, I used QuantumATK 2018.06-SP1-1.
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General Questions and Answers / the average Hartree difference potential under an external electric field
« on: October 24, 2019, 08:45 »
Recently, I read an article (Nano Energy, 2019, 63, 103863)，in which a methodology named OPNS (one probe and non-equilibrium surface Green’s function) was mentioned. Figure 1 herein shows that the average Hartree difference potential is perturbated by an external electric field. But in my tests, the average Hartree difference potential showed the same shape under different external electric fields. I want to know if there is something wrong with my calculation settings. I hope someone can help me.
Any help would be greatly appreciated.
Any help would be greatly appreciated.
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General Questions and Answers / Re: How to build electric field
« on: November 5, 2014, 02:02 »
Thank you very much!
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General Questions and Answers / How to build electric field
« on: November 4, 2014, 18:16 »
Hi All,
I’d like to study the I-V character of Fullerene under electric field. But I do not know how to build the device. Should the electric field just apply on the central region, or should apply on whole device? Which one is correct? In addition, should I add a dielectric region above the metallic region?
Any help on this problem would be greatly appreciated!
I’d like to study the I-V character of Fullerene under electric field. But I do not know how to build the device. Should the electric field just apply on the central region, or should apply on whole device? Which one is correct? In addition, should I add a dielectric region above the metallic region?
Any help on this problem would be greatly appreciated!
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General Questions and Answers / Re: How to set the initial spin for a fullerene molecule?
« on: March 26, 2013, 15:39 »
Thank you very much! I will read it.
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General Questions and Answers / Re: How to set the initial spin for a fullerene molecule?
« on: March 19, 2013, 14:19 »
Thank you very much! The sqrt(n) method is taken from http://en.wikipedia.org/wiki/Magnetic_moment, the original form of it is M=g*(J*(J+1))^0.5, where J is the total angular momentum quantum number, g is the Landé g-factor. For free electron, g~2, so it change to M=(n*(n+2))^0.5, where n is the number of unpaired electron. So, what is the diffrent between the two magnetic moments calculated by subtract the spin up populations from the spin down populations and this method?
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General Questions and Answers / How to set the initial spin for a fullerene molecule?
« on: March 19, 2013, 09:31 »
Dear, I’d like to repeat a work published on the Chem. Phys. Lett. (2012, 535, 111-115) which reported the transport spin polarization of fullerene C28 (Td). But there are two problems need somebody’s help.
1.How to set the initial spin for this device? C28 (Td) has four unpaired electrons, what should I do to initialize the configuration in a SGGA calculation?
2.How to calculate the magnetic moment of one atom like reported in this work? I have noticed the answer form @zh like M = population-up - population-down. But for the example in http://quantumwise.com/publications/tutorials/mini-tutorials/141, the spin up population is 6.788, and the spin down population is 5.573 for the Vanadium atom, so the M should (6.788-5.573=1.215), why the result in this tutorial is 1.251? According another method to calculate the magnetic moment (M=(n*(n+2))^0.5), the result for this atom will be 1.97. What is the deferent between them?
1.How to set the initial spin for this device? C28 (Td) has four unpaired electrons, what should I do to initialize the configuration in a SGGA calculation?
2.How to calculate the magnetic moment of one atom like reported in this work? I have noticed the answer form @zh like M = population-up - population-down. But for the example in http://quantumwise.com/publications/tutorials/mini-tutorials/141, the spin up population is 6.788, and the spin down population is 5.573 for the Vanadium atom, so the M should (6.788-5.573=1.215), why the result in this tutorial is 1.251? According another method to calculate the magnetic moment (M=(n*(n+2))^0.5), the result for this atom will be 1.97. What is the deferent between them?
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General Questions and Answers / Is this configuration reliable?
« on: February 27, 2013, 08:22 »
I'd like to study the tranport properties of one fullerene cage with gate voltage, a device was built as the attachment, and Neumann will be act as the boundary condition. However, I'm not sure whether it is reasonable. Can someone help me?
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General Questions and Answers / Re: thermal relaxation and dephasing
« on: January 17, 2013, 12:23 »
Thanks for your help. Is it satisfying if I say like this?
From the width of the transmission peak (w), we can get the coupling strength, γ, about w/2. If kT<<γ, dephasing is not important. The calculated transmission by ATK is based on the first-principles, and the results show the properties of the studied systems under the temperature T=0 K. The coupling strength of the transmission peak close to the Fermi level is 0.2 eV, and T<<r/k=2.32*10^3 K. Therefore, relaxation and dephasing are not expected to play a role for the structures under study here.
From the width of the transmission peak (w), we can get the coupling strength, γ, about w/2. If kT<<γ, dephasing is not important. The calculated transmission by ATK is based on the first-principles, and the results show the properties of the studied systems under the temperature T=0 K. The coupling strength of the transmission peak close to the Fermi level is 0.2 eV, and T<<r/k=2.32*10^3 K. Therefore, relaxation and dephasing are not expected to play a role for the structures under study here.
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General Questions and Answers / thermal relaxation and dephasing
« on: January 16, 2013, 08:43 »
I had calculated some molecular devices based on fused oligothiophenes. For my results, one reviewer said that:
" In Figure 3, there are peaks close to or at the Fermi energy in the zero voltage transmission plots. This may lead to longer tunneling times and thus to an interaction between the tunneling electron and the molecules nuclear degrees of freedom, which may make the Landauer picture little suitable for describing electron transport through the bridge since thermal relaxation and dephasing may become dominant. The authors may wish to either mention this issue (citing, e.g., A. Nitzan, Annu. Rev. Phys. Chem., 2001, 52, 681-750) or discuss why relaxation and dephasing are not expected to play a role for the structures under study here."
This reference is a long review and fulled of physical equation, and I have no idea about it. Could someone help me?
" In Figure 3, there are peaks close to or at the Fermi energy in the zero voltage transmission plots. This may lead to longer tunneling times and thus to an interaction between the tunneling electron and the molecules nuclear degrees of freedom, which may make the Landauer picture little suitable for describing electron transport through the bridge since thermal relaxation and dephasing may become dominant. The authors may wish to either mention this issue (citing, e.g., A. Nitzan, Annu. Rev. Phys. Chem., 2001, 52, 681-750) or discuss why relaxation and dephasing are not expected to play a role for the structures under study here."
This reference is a long review and fulled of physical equation, and I have no idea about it. Could someone help me?
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General Questions and Answers / Re: help!!!how can I address the transport properties around the Fermi level
« on: November 30, 2012, 11:02 »
Thank you! I'll try it.
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General Questions and Answers / help!!!how can I address the transport properties around the Fermi level
« on: November 27, 2012, 08:54 »
I have do some calculations about a two-probe system, the transmission spectrum showns that there is a peak at 0.12eV in the zero voltage. However, according to the MPSH analysis, the energy of LUMO state is 2.20 eV, far from the Fermi level, and the energy of HOMO state is -0.18 eV, So, how can I address this peak? Someone told me that the LDOS analysis maybe do it ,but I do not know what information can be read from the LDOS. I post the results here with the hope that someone can help me.
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General Questions and Answers / Re: NameError: name 'zero_bias_potential' is not defined
« on: December 20, 2011, 15:51 »
Thank you very much. Now, it work well.
But I have another question, in the tutorial at http://quantumwise.com/publications/tutorials/mini-tutorials/98, we do a I-V SCF calculation for lih2li at [0., 0.1, 0.2, 0.3]*Volt, why the bias in I-V curve is [-0.3,-0.2,-0.1,-0.]*Volt?
But I have another question, in the tutorial at http://quantumwise.com/publications/tutorials/mini-tutorials/98, we do a I-V SCF calculation for lih2li at [0., 0.1, 0.2, 0.3]*Volt, why the bias in I-V curve is [-0.3,-0.2,-0.1,-0.]*Volt?
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