Messages

16

General Questions and Answers / Re: A question about transmission pathway

« on: June 23, 2018, 13:40 »

         Thanks! I have understood  the first question  with your kind help . However, I am still confused by the second question.
          Fig. 1(a) and Fig. 1(b) are spin-resolved transmission spectra under zero bias voltage for device-A and device-B, respectivley.  From Fig.1(a) and Fig.1(b), it can be seen that transmission peak for device-B at E=0.25 eV  is larger than that for device-A.  Therefore, I want to use transmission pathway to explain why the value of transmission peak at E=0.25 eV for device-B is larger than that for device-A.   The calculated transmission pathway for device-A is shown in Fig.2(a) and for device-B is shown in Fig.2(b).  Plotting parameters for Fig.2(a) and Fig.2(b) are the same and  displayed in Fig.3.  Obviously, compared to Fig.2(b), Fig.2(a)  shows much more backscattering transmission (red arrows) in center molecule.  Could I say  such backscattering transmission leads to lower transmission peak for device-A than device-B at E=0.25 eV? 

17

General Questions and Answers / Re: A question about transmission pathway

« on: June 20, 2018, 06:56 »

can anyone help me?

18

General Questions and Answers / A question about transmission pathway

« on: June 19, 2018, 09:26 »

Dear Qunantumwise Staffs:
         In VNL, threshold in transmission pathway is described as "only include scaled tranmission above the given threshold. The transmission t are scaled as (t/tmax)**ρ, where ρ is the scaling power."  So scaled transmission t_scale= (t/t_max)**ρ. I notice that the default  ρ is 0.00. What does it mean? Let's take the example,  if  local bond transmission between atom A and atom B  t=0.4,  the t_max=1, when default  ρ is 0.00, the scaled transmission   t_scale= (t/t_max)**ρ=(0.4/1)**0=1.  That's to say, for all transmission pathway,   when  ρ is 0.00, t_scale always equals to 1 and the threshold doesn't make sense in that case. Should I set ρ=1.00?   In addition, from the definition of scaled transmission, the radius of arrow seems the relative value ( (t/t_max)). Does it mean that I can't compare conductance of two different devices? 

19

General Questions and Answers / Re: a unexpected tranmission dip at fermi level

« on: April 2, 2018, 02:27 »

thank you for your help！

20

General Questions and Answers / a unexpected tranmission dip at fermi level

« on: April 1, 2018, 09:15 »

Dear Quantumwise staffs:
            I construct a device using (4,4) carbon nanotube(CNT) as electrodes connecting to carbon atoms chains and calculate transmission spectra. (Mesh-cutoff I select is 100 hatree and k-point is 1*1*100. The functional is spindependent GGA-PBE). However,  there are sharp transmission dips at fermi level  whether bias voltages are applied nor not .  It's well kown that (4.4) CNT is metallic and there is no bandgap around fermi level.  I can't figure out why there are unexpected dips in transmission spectra, can anyone help me?
           Best
          P.S  Fig.1 is calculated transmission specta at 0V, and Fig.2 is contact types of device I construct.

21

General Questions and Answers / Re: Can ATK calculate optical properties of system?

« on: February 2, 2018, 01:48 »

thanks for you help. sir. I'll look iinto these

22

General Questions and Answers / Can ATK calculate optical properties of system?

« on: February 1, 2018, 14:15 »

Dear Quantumwise staffs:
           One of my colleague wanna know can ATK calculate optical properties such as adsorption wavelength, emission wavelength, etc. I can find there is "opticalspectrum" in analysis term for bulk configuration. I don't know whether it is  what he wants. Do you have tutorial about how to calculate optical properties?
           Best

23

General Questions and Answers / Re: why is my density of states not smooth？

« on: January 25, 2018, 02:38 »

thanks for your help！

24

General Questions and Answers / Re: Can we optimize a portion of atoms along certain directions in ATK.2015?

« on: December 19, 2017, 14:39 »

thank you, i will try

25

General Questions and Answers / Re: Can we optimize a portion of atoms along certain directions in ATK.2015?

« on: December 18, 2017, 01:35 »

can anyone help me, please?

26

General Questions and Answers / Re: Can we optimize a portion of atoms along certain directions in ATK.2015?

« on: December 14, 2017, 09:32 »

thanks for your reply .  But in VNL (ver.2015), it seems there is no option for optimizing or fixing some atoms of the system along particular directions (shown in fig1). For example, the structure contains 6 atoms numbered by 1, 2, 3, 4, 5, 6, respectively. I want to optimize atom 1 and atom 3 along the x direction,keeping the others fixed. Can I do it using VNL-ATK 2015?   How do I modify the input script to realize it ?

by the way,  I want to request a license for academics from this link: https://quantumwise.com/free-trial/free-vnl. But It  still doesn't work. The trial license has been out of date.  How do I request licenses?

Best

27

General Questions and Answers / Can we optimize a portion of atoms along certain directions in ATK.2015?

« on: December 8, 2017, 10:46 »

Dear Quantumwise staffs:
           Should we optimize the part of atoms in the system along the certain direction in ATK.2015?  For example: there are 5 atoms in the system, numbered by 1, 2, 3, 4, 5.  I just want t o relax atom 1, 2  along the x, y direction and keep z fixed. Other atoms also keep fixed.  How do I do that?
Best

28

General Questions and Answers / why is my density of states not smooth？

« on: October 15, 2017, 13:57 »

    Dear scholars, I have a question about ATK (ver.2015). Now I want to look at the hybrid configuration at spinterface between BDT molecule and Nickle. And I used slab model to simulate interface, which is subjected to present conditions. The trouble matter is as follows:
When I calculate density of state of BDT contacting on Nickle, the image is not smooth.
    I used builder to build its slab model, and then I optimized the bulk and added the analysis of density of state to script.Please look at script1.And follow this I calculate its density of state, but the result is not good. The image of DOS is not smooth prospectively. Please look at image1. I try many methods to change this situation, trying to increase k-polint sampling to 9*9*1, increasing vacuum size to 20, I just hope the DOS of energy-independece image be smooth. However I didn’t find the real reason to avoid this. What good method could solve this trouble?Being more smooth by this slab simulating?
      Best
 

29

General Questions and Answers / How does ATK obtain charge distribution on individual atom in *.out file?

« on: September 8, 2017, 14:46 »

Dear Quantumwise staffs：
          When we finish scf, we can get *.out file that reports charge distribution on every atom like figure1 (rectangled by black lines). I wonder how does ATK justice which electron belong to which atom? Are these distribution the same with  Mulliken population or not? Can I use these data to calculate net magnetic moment? 
Best

30

General Questions and Answers / Re: Differences between electron density calculating using DZP and SZP

« on: June 18, 2017, 10:33 »

Thanks for your guide！ I have solved the problem by extending chentral region as you said.