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Messages - rebeda

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16
General Questions and Answers / Re: Thermoelectricity as a function of temperature
« on: March 8, 2018, 13:36 »
Thank you very much for your quick reply.  Could we get the respective NanoLanguage script sometime soon? It would then be of immense help to us.

Regards,
Rebeda

17
General Questions and Answers / Thermoelectricity as a function of temperature
« on: March 7, 2018, 13:29 »
Calculating thermoelectric  coefficients in the "vnl" window under the "thermoelectric  coefficients" calculator is a time consuming process as I need to extract all the thermoelectric  coefficients at various temperature (10 to 600K )for 12 molecular junctions.

So, I downloaded a python script (attached below)  from forum for extracting all the thermoelectric coefficients at temperature upto 600 K.

When I executed the script, the thermoelectric coefficients (such as conductance , thermopower, ZT , Peltier cofficient and electrical thermal conductance ) extracted were not the same compared to the coefficients calculated from the vnl window...

Will you please help me.
Regards,
Rebeda

18
General Questions and Answers / Re: Transmission projection
« on: December 22, 2017, 06:29 »
Thank you Petr  :)

When will the new version be released ???? How long do I have to wait??? :-\

Thank you,
Rebeda

19
General Questions and Answers / Re: Transmission projection
« on: December 16, 2017, 14:50 »
Hi Petr,
  I have calculated  "mpsh.nc" file  following the updated link you have suggested. But, I could not get "+-isovalue" while analyzing the nc file in viewer located under -
 vnl>>viewer>>scene properties>>isosurfaces.

 I am not able to tick the "+- isovalue" dialogue box in the  "scene properties" panel.

Regards,
Rebeda

20
General Questions and Answers / Re: Transmission projection
« on: December 16, 2017, 10:27 »
Dear Petr,

Thank you so much for your help. it indeed worked!!!!!!!!!! :D

But I am facing some technical problems in analyzing the + - isovalue  in the viewer. I faced the same problem while viewing the eigenstates  calculated using the updated ATK vnl versions. (may be due to big file )

Can you please help me ... :-\ :-\ :-\

Regards,
Rebeda

21
General Questions and Answers / Transmission projection
« on: December 15, 2017, 08:17 »
Dear Sir,
Following the script files given in the link : https://quantumwise.com/documents/tutorials/latest/LowLevelEntities/index.html/chap.transmissionprojection.html

I performed transmission projection calculation for my system using ATK Vnl 2015.1 . But I have encountered some problems while executing the mpsh.py file. Given below:-

+------------------------------------------------------------------------------+

Timing:                          Total     Per Step       

--------------------------------------------------------------------------------

File IO, nlread         :      28.17 s      14.09 s      49.90|=============|
Loading Modules + MPI   :       3.99 s       3.99 s       7.06|=|
--------------------------------------------------------------------------------
Total                   :      56.47 s
eigen energy  123 -3.96173022816 eV
Traceback (most recent call last):
  File "mpsh.py", line 65, in <module>
   
  File "A:\Softwares\vnl\projection\3co\utilities.py", line 79, in vectorToGrid
    vectorBoundaryConditions(boundary_conditions),
NameError: global name 'vectorBoundaryConditions' is not defined


I have attached the related python files which I created for my system {AuNW(111)-Co3(dpa)4(SCN)2-AuNW(111)}.

Will you please help me  :-[ :-[ :'( :'( :-\ :-\ :'( :'(

Regards,
Rebeda

22
General Questions and Answers / Re: Negative inelastic transmission
« on: November 16, 2017, 06:17 »
Dear Sir,

I got confused wether it is quasi-harmonic approximation or simply harmonic approximation?

Another small querry: how strongly the results of IETS(XLOE) in molecular junctions are supposed to depend on the exchange-correlation function ?
Thank a lot for your reply.

Regards,
Rebeda

23
General Questions and Answers / Re: IETS calculations - reg.
« on: November 15, 2017, 13:19 »
Dear Sir,

In the IETS calculation were the vibrational normal modes evaluated in the harmonic approximation? If not, what type of approximation was used (ATK vnl 2015.1) ?

Awaiting your reply.

Regards,
Rebeda

24
General Questions and Answers / Re: Problem arising with the arrival of new atk-vnl versions - reg.
« on: July 12, 2017, 13:53 »
Dear Sir,

It is great that atk-vnl is upgraded everytime with the upcoming of every new versions. But one big problem is that, we are not able to access the new versions with the previous  xxx.nc files calculated from lower versions. Some of the device calculations are time consuming and we rather not repeat the same calculations in the new versions. Due to it we are not able to utilize some of the new upgraded features which may help in better analysis of our calculated datas. Would you suggest a way to solve this issue??????

Waiting for your response.

Regards,
Rebeda

25
General Questions and Answers / thermoelectric transport properties in vnl window - reg.
« on: June 28, 2017, 07:12 »

As I have mentioned before seebeck effect is realized when there is a temperature difference (in our two probe system, the electrodes are maintained one at cold TCand other at hot TH temperature ). And ZT is directly proportional to seebeck coefficient by formula.

So, My question is, when ATK perform thermoelectric coefficient calculations , what TC /TH value it takes ?

As an example, when we want to find ZT experimentally using STM, the STM tip and the sample are maintained at different temperatures, one at cold (TC) and other at hot (TH) temperature. In this case the tip is (TC) and the sample temperature is (TH).

Similarly, in atk theoretical calculations TC  and TH must be assigned with some temperature values in which we keep on changing one of the temperature (say TH ) to calculate thermoelectric coefficients at variable temperature.

I hope you might understand my question. I have added some link of articles to help undestand the problem.

http://www.pnas.org/content/112/27/8205.full.pdf
http://dx.doi.org.sci-hub.ac/10.1063/1.4958999

regards,
Rebeda

26
General Questions and Answers / thermoelectric transport properties in vnl window - reg.
« on: June 27, 2017, 11:26 »
Thank you so much for your reply it cleared my doubt. :D :D :D

T=(TH + TC)/2. 
In the above formula either TC or TH are kept constant in the entire atk calculations . If so, what is the constant temperature value?
 I need these values to calculate the maximum effeciency.

Is TC = 4.2K (liquid helium temperature) or TC = 0K ?????

Awaiting for your useful comments.

Regards,
Rebeda

27
General Questions and Answers / thermoelectric transport properties in vnl window - reg.
« on: June 27, 2017, 10:28 »
Thank you  Daniele Stradi for your quick response.

The T in the formula is introduced to make it a dimensionless value figure of merit "ZT". Usually thermoelectric behaviour is achieved when we make a temperature gradient/difference. In our case (two probe junction) the two electrodes are maintained one at cold (TC) and the other at hot (TH) temperature.

So, when we enter the temperature values to calculate the thermoelectic coefficients (in the vnl window) is -
         
1. T = TH-TC  ?
or
2. T=(TH-TC)/2 ?

Lastly, in atk calculations  what are the values of TC and TH ?

Awaiting for your kind reply.

Regards,
Rebeda

28
General Questions and Answers / thermoelectric transport properties in vnl window - reg.
« on: June 27, 2017, 07:18 »
Dear sir,
I have some confusion on the thermoelectric transport properties in vnl window. What does T really stand for???

1. does it stand for average temperature (an average of hot and cold electrodes temperature of the two probe device)?
2. does it stand for the environment temperature of the device?

looking forward to your reply.

regards,
Rebead

29
General Questions and Answers / Re: Negative inelastic transmission
« on: November 9, 2016, 14:08 »
Dear Sir,
 
Thank you so much for your reply.
In one of our systems we come across inelastic transmission ranging from -10 to +10 for both symmetric and asymmetric contributions due to certain phonon mode .This way the inelastic contributions comes 10 times of elastic contribution. Could you please help me to interpret it?

Awaiting for your kind reply.

Regards,
Rebeda

30
General Questions and Answers / Negative inelastic transmission
« on: November 8, 2016, 14:27 »
Dear Sir,

According to my knowledge transmission, being a probability, can have minimum value of 0 and maximum of 1 (though it depends on the no. of channels available for conduction) and hence,  is always positive, but refering to one of your quantumwise tutorial-
link: http://quantumwise.com/support/tutorials/item/877-inelastic-electron-spectroscopy-of-h-molecule-between-1d-au-chains
I observe negative inelastic transmission at mode 0 and mode 5 in the IETS study of H molecule between 1D Au chains. I am not able to interpret this "negative inelastic transmission". In other words, how transmission can have negative values in this case, though for IETS, one can understand to have both positive and negative values.
Will you please help me?

Regards,
Rebeda :( :( :(

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