Topics

1

General Questions and Answers / MPSH orbital denisty

« on: August 2, 2015, 01:47 »

Dear All ,
Can i measure the orbital density of MPSH on the clips atoms of an two- probe system???
Regards,
Khattab 

2

General Questions and Answers / level alingment

« on: August 2, 2015, 01:43 »

Dear All,
I carried out some electron transport calculations and when i summit the manuscript, i got the following comment,

1- There is no discussion of the incorrect level alignment resulting from an LDA calculation, that is routinely corrected in similar calculations in the literature 
 How can reply to this comment,
Any help???
Regards
Khattab

3

General Questions and Answers / HOMO & LUMO Idetification from MPSH energy spectrum

« on: December 11, 2014, 03:18 »

Dear All,
I read all posts about this topic, how to identify HOMO & LUMO energy from MPSH energy spectrum . i read Dr Anders Blom about this topic in this link,
http://quantumwise.com/forum/index.php?topic=185.msg1050#msg1050
as dr anders say , by definition the HOMO has the highest negative energy and the LUMO the lowest positive energy.
What about HOMO-1 or LUMO+1 
My system have 40 shell electron which mean orbital no 20 is HOMO and orbital no 21 is LUMO when i calculate MPSH spectrum and project it on molecule only, i got results in the attached file.
Now i want to ask few questions
1- How to identify HOMO, HOMO-1, LUMO, LUMO+1 and so on
2- what are this many values some are positive values (+) and the other are negative value (-) 
3- for my information i have 40 valence electron so i have only 40 values have of them for 20 occupied orbitals and the later half for 20 unoccupied orbitals, (Am right or not)
waiting for your answer as soon as possible,
Thanks in Advance,
Khattab 

4

General Questions and Answers / Bias window identifcation help

« on: November 4, 2014, 13:57 »

Dear All,
Now, i calculated I-V curve of some organic molecules, and i want to interpret these curves with the aid of transmission spectrum curves, i read all questions about transmission spectrum and bias window in quantum forum and i clearly understand that the current is the integration of transmission spectrum at given voltage, and the integration limits are chemical potential for left and right electrode this according to Landauer-Buttiker formula , now when i calculated the transmission spectrum at 4 volt i set the voltage of one electrode at 0 volt and the voltage of the other electrode is 4 volt in this case, what is the bias window for this cas and  how can i identify bias window at the transmission spectrum curve  ?
Waiting for your replay as soon as possible,
Thanks in advance,
Khattab

5

General Questions and Answers / Dos interpretation help!!!

« on: September 24, 2014, 13:59 »

Dear All,
Now i calculate I-V curve of some two probe systems, but i couldn't know the difference between different curves, so i calculate Dos but i want to interpret its curves, could any one help me to know what is Dos  ???and how can i us it to interprete different I-V curves
Thanks in Advance ,
El-Sayed Khattab 

6

General Questions and Answers / Relaxation problem

« on: June 23, 2014, 17:07 »

Dear All,
I want to relax a tow probe system, my system consist of two rings but the process is very slowly , can any one guide me how to relax this system simply , how can i set the parameters of relaxation like Force tolerance and Trust radius to make the process fast
Note:- i study trend between some molecules so i don't care about accuracy, only i want to relax these molecules before i study some parameters.
Any help please   
Kind Regards,
Khattab

7

General Questions and Answers / I-V Curve of BDT Device

« on: April 26, 2014, 17:19 »

Dear All,
I want  to calculate Some parameters for BDT , so recalculated the I-V curve and Transmission spectra for BDT and compared them with reference paper ( Computational Materials Science 27 (2003) 151-160), Transmission spectra curve i calculated is in a good agreement with the published curve in Fig(2) in the paper, but unfortunately  I-V curve i calculated is not Like published curve in Fig (4) in the paper.
The attached file is the curve i calculated.
Could anyone  Help me please 
Kind Regards,
Khattab

8

General Questions and Answers / Number of cores

« on: March 29, 2014, 17:24 »

Dear All,
Kindly, i running ATK on workstation which has 8 core, i want to know the number of cores used for each process.
Kind Regards,
Khattab

9

General Questions and Answers / I-V curve of BDT divese

« on: March 19, 2014, 16:10 »

Dear All ATK Stuff
Firstly, i am sorry for my very simple question but i am still new beginner. 
I redid the calculation of transmission spectrum and I-V curve for DTB(Dithiol benzene) which calculated in the paper [ Computational Material science 27 (2003) 151-160] figure 2 and 4. when searched ATK forum i found the same question in the forum on this link http://quantumwise.com/forum/index.php?topic=1617.0
when i calculate transmission spectrum the curve i get went  i good agreement with the curve in the paper, when i tried to calculate I-V curve in the same range from 5.6 to -5.6 volt and interval is 0.1 like the paper, i set the parameters as K point (1,1,500) and number of points 113 point . i didn't get a curve but when i drop the vnl file in the result browser i get this message ( Current: 3.06014542552e-009 A)

My questions are:-
Q1:- Why i didn't get a curve??
Q2 :- IF this mean that i should calculate the current for each voltage separately, if this is true how can i do this, and how can i set the values of left electrode and right electrode  ?
note :- the attched file is the output file for I-v calculations
Kind Regards,
Sayed
 

10

General Questions and Answers / Relaxation question

« on: March 17, 2014, 10:34 »

Dear All,
How can i relax my two probe system before starting calculations on it.
Regards,
Sayed

11

General Questions and Answers / Transmission spectrum error

« on: March 14, 2014, 05:11 »

Dear All
I want to calculate some parameters like transmission spectrum and density of state for a two probe system by ATK, i carried optimization on gaussian 09 then, i calculate the transmission spectrum and DOS by ATK and i get the normal termination, when i want to optimize the structure by ATK  in order to relax the structure and began the calculation from the check point file of the optimization i get different curve for DOS than the 1st curve of DOS, for transmission spectrum  the values of all transmission coefficients is zero  which also different than the 1st curve. My questions are:-
1- If the optimization affect on the values of DOS and Transmission spectrum ?
2- How can i relax the system on ATK??

Note:- i use  version  2008.10 of ATK
Regards,
Sayed