Messages

1

General Questions and Answers / Re: direction of flow of current

« on: April 29, 2013, 00:33 »

Dear Anders,

If the left electrode is at lower potential than right electrode, why the manual is saying that the direction of current is from left to right?? The current flow from higher potential to lower potential. Is it trying to  say that the flow of electrons is from left electrode to right?? Generally we know that current direction and flow of electron is opposite. This things is confusing me. Can you please elaborate??


Regards,
Anjana

2

General Questions and Answers / direction of flow of current

« on: March 28, 2013, 03:03 »

In a two probe device IV calculation, what is the direction of flow of electron,when it is at positive bias

Left electrode chemical potential  =   -2.387412 eV                          |
|Right electrode chemical potential =   -2.287412 eV 

Regards,
Anjana

3

General Questions and Answers / Re: some question about the transfer charge

« on: March 1, 2013, 21:48 »

Hello everyone,
 
    Recentlly, I investigate the effect of gate voltage on electronic transport properties in
a molecular device. I obtains the transfer charge and the equilibrium conductance with different gate
voltage. What's mean of the positive and  negative value of the transfer charge ? In other's paper, they think the positive value means that electrons are transferred from the electrode to the cluster. (Dai, et al.PHYSICAL REVIEW B 73, 045411 2006) Is it good for transport properties or not ? How do i understand the change of  the transfer charge and the equilibrium conductance with  gate voltage in the figure?

Thanks!

4

General Questions and Answers / Re: unsymmetrical density of transmission eigenstate around left and right electrode

« on: February 19, 2013, 20:41 »

Thank you so much for the reply. But in some cases, even I select the contribution form the left, I see good density around the right side, like in the attached figure. What might be difference in these two cases.

5

General Questions and Answers / unsymmetrical density of transmission eigenstate around left and right electrode

« on: February 18, 2013, 18:46 »

I have noticed that, the density of transmission eigenstate around left and right electrodes are not symmetrical, even for symmetrical molecules. And, it is always seen that the density in left electrodes is quite high than in the right electrodes, even though the contact molecules attachment is same on the both side. This thing is really confusing me. And I believe this is the reason why I am getting low  value of transmission spectrum. I have been trying to analyze the IV curve for the cages with thiophene. I have attached the relevant figures. Somebody please help me on this

Regards,
Anjana 

6

General Questions and Answers / Re: spin in two probe calculation

« on: September 27, 2012, 17:49 »

Thank you so much for the reply. So how do I constrain spin to a particular molecular configuration??

7

General Questions and Answers / spin in two probe calculation

« on: September 27, 2012, 00:23 »

Is it possible to give spin state (such as +1/2, 1,+3/2,2, 5/2) to a particular atom in two probe calculation ( for generating IV curve). For example in my calculation, I require to have transition metal which are generally stable with some net spin electrons. So how can we build that kind of system

Thanks in advance,

Anjana

8

General Questions and Answers / Re: calculate IV curve for charged molecules

« on: September 18, 2012, 02:06 »

Actually I am trying to calculate the current through carborane cage with dithiophene .I have attached the structure here. With gaussian calculation, it came out that the structure has stable state with charge=-3 and spin =0; And now I want to calculate current through it using atomistix. I want to use the optimize structure from gaussian calculation, including the charge, which makes the molecule stable. This is why i needed to add some charge in the central region (and not even in the contacts). What can I do to realize this system  What is the use of externalpotential() function, that is included in atomistix?? will that be helpful??

9

General Questions and Answers / Re: calculate IV curve for charged molecules

« on: September 17, 2012, 19:41 »

Ok. That seems to make some sense. So if my molecules in the device region has three extra electrons, can I assign the gate voltage to be -3 eV, and do the device calculation??

10

General Questions and Answers / calculate IV curve for charged molecules

« on: September 16, 2012, 23:38 »

I want to calculate the IV curve for a molecule which is charged. In the two probe calculation, I did not see any options for charge insertion. I even tried to include some charge inside the LCAO calculator, but it generated errors. Does that mean I cannot obtain the IV curve for a system wherein the  molecule in the device region has some charge???

11

General Questions and Answers / very slow calculation

« on: September 11, 2012, 04:53 »

I am using the demo version of atk 12.2.2. I am running the atomistix in a cluster. But the calculation are really slow, as if in a normal computer. I tested the parallelization with the test_script file, and it is perfectly fine. What might be the problem? Is it because I am using the demo version in a cluster?? or something else???


Anjana

12

General Questions and Answers / input file work for 4*4 (111) gold surface but not for 5*5 (111) gold surface

« on: July 19, 2012, 08:35 »

I am trying to calculate the IV curve for the following system. This works  fine when I use 3*3 gold atoms layers(electrodes) but not with 5*5 gold atoms layers. What might be the problem. The simulation keep running but there is no updates...is it the problem with the K point. I used 1,1,10 k points for both the system,. It works for 3*3 but not for 5*5.
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13

General Questions and Answers / is it possible to calculate IV for such molecules

« on: July 5, 2012, 22:27 »

I was wondering if one could obtain the IV curves for the molecules shown in picture.  the molecules is optimized. If so how are the elctrodes and contact placed??