Messages

61

General Questions and Answers / Re: Question about molecular energy spectrum in two-probe

« on: November 21, 2012, 11:07 »

 my description is not clearly

Generally speaking, in device system, the electrons occupying of LUMO(MPSH) is nearly 0,

whether the LUMO(MPSH) near Fermilevel, the electrons occupying of LUMO(MPSH) is not zero, like this system?

how do we define the MPSH (HOMO or LUMO) in device system? electrons occupying or positive and negative energy(energy zero is Fermilevel of electrode)?

Regards

62

General Questions and Answers / Re: Question about molecular energy spectrum in two-probe

« on: November 21, 2012, 10:05 »

thank you professor Anders, it is to say if the LUMO near Fermilevel, the electrons occupying of LUMO is not zero

63

General Questions and Answers / Question about molecular energy spectrum in two-probe

« on: November 21, 2012, 08:47 »

Dear QuantumWise staff:

i calculate the  molecular energy spectrum in two-probe, the energy zero is Fermilevel, i will upload the energy spectrum in the attcherment.

the orbital of 109 is LUMO, but there are still almost one electron? why?

  Au electrode consists of a (5×5) supercell, T=300K, the K-point 3*3*100, it is enough to correctly describe  Fermilevel.

64

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 19, 2012, 15:25 »

thank you professor Anders, i will change the scattering region.

so sorry to waste your time

regards

65

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 19, 2012, 14:58 »

TE is different in different bias, and it changes a lot, it may be wrong to obtain i-v using zero-bias TE. under low bias 0-0.9V, the current is zero, the method is right, as shown in fig1, integration is always 0.
but higher than 0.9V, the integration will increase a lot.

fig2 shows TE in 0.9, the integration is 0. 

it is inconsistent

66

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 19, 2012, 14:16 »

thank you professor Anders

the band gap of graphyne nanoribbon is 1eV, during 0-1V, the current is almost 0, not a liner i-v, see fig, the TE changes a lot with the increasing of the bias, i think the method will be wrong during the 1.1-2V or higher.

67

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 19, 2012, 12:55 »

i'm so sorry about that professor Anders

but i have read some of papers studying transport property of graphenenanoribbon, such as APPLIED PHYSICS LETTERS 94, 173110,  JOURNAL OF APPLIED PHYSICS 110, 013718,  J. Phys. Chem. C 2012, 116, 5915−5919,

both of them studied transport property of nanoribbon as shown in fig1 and fig2 (J. Phys. Chem. C 2012, 116, 5915−5919), they report perfect  transport property of ZGNR junctions and i-v curse shown in fig2

i just want to simulate the effect of different edge to the transport property under different bias, is that pointless?

Regards

68

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 19, 2012, 01:36 »

thank you professor Anders, this is my system, i think it is enough for the center scattering area and electrode, but it still hard to converge in higher bias(more than 1.1V), why?

the band gap of the electrode is about 1eV, so i should decrease the electrode temperature, because Fermi broadening is useless for the electron occupied in the band gap. Maybe this will lead to misconvergence. am i right?

69

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 18, 2012, 04:03 »

or using LDA instead of GGA, is that LDA converged better than GGA?

70

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 18, 2012, 01:58 »

i increase the history steps to 30(my Cluster can't sustain more than 35) and mesh cutoff to 200Ry, but it doesn't work. what should i do? Can i use electrode constraint? is it helpful?

71

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 14, 2012, 02:21 »

atk 11.8.2-linux
 Is that the convergence of 12.2 better than 11.8?

72

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 13, 2012, 15:12 »

thank you professor Anders, i increase the central region (quadruple the electrode), under the low bias it converge well, but when the bias is 1.4V, it is still hard to converge, should i use electrode constraint? maybe the electrode constraint (DM) can lead to converge?

73

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 13, 2012, 04:26 »

thank you professor kstokbro

 i use real_axis_point_density to 0.005eV, it still hard to converge at bias 0.9V(dH is hard to converge), should i increase bias contour points to 50-70?

or i should increase the scattering region, my scattering region is the same length as cell of electrode. should i double the scattering region?

74

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 12, 2012, 08:45 »

Thank you professor Anders, i also increase the history step to 15, but for my system it did't work well under bias.

Actually, my system indeed converge  more than 350 steps when the bias higher than 0.4V, it cost lots of time. could you give me some advices to speed up the convergence?

another question: Do lower the real_axis_point_density  change the results? i mean the transmisson spectrum

75

General Questions and Answers / Re: how to use preconditioner Kerker for convergence?

« on: November 12, 2012, 08:06 »

thank you so much professor kstokbro

there is no warnings in the logfile, i'll try to lower the real_axis_point_density to 0.005eV(double contour integral).

another question: Do lower the real_axis_point_density  change the results? i mean the transmisson spectrum

Regards