Messages

16

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

« on: December 15, 2014, 20:44 »

Dear dr umberto
Thank you very much for your reply; I understand what you say,  but the attached log file is all results that I got when I calculate mpsh energy spectrum. What can I do niw?
 Waiting for your help as soon as possible
Thanks in advance
Khattab

17

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

« on: December 12, 2014, 10:41 »

Dear dr anders blom,
 Thank you very much for your reply ،  I always waiting for this; you said in past post that homo energy is the highest negative value and lumo is the lowest positive value,  are this true???
How can l get occupation?
Waiting for your answer as soon ss possible
Thanks in advance
Khattab

18

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

« on: December 11, 2014, 23:12 »

Dear Dr Umberto Martinez,
Thank you very much for your replay, but what i want to know is how to identify HOMO, LUMO, HOMO+1, LUMO-1 from MPSJ energy spectrum i attached,not to know their quantum numbers.
Thank you,
Khattab

19

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 

20

General Questions and Answers / Re: Bias window identifcation help

« on: November 11, 2014, 09:02 »

Dear dr  anders blom,
Thank you very much for you time and your effort to reply my questions ,  now I clearly understand that in simple cases like two probe system in order to idenyify bias window  we divide voltage of left and right electrode by 2.
Thank you very much
Khattab

21

General Questions and Answers / Re: Bias window identifcation help

« on: November 8, 2014, 08:38 »

Dear Dr Anders Blom,
Firstly thank you very much for your rapid response of my questions, I read the page you sent , and this is the part about bias window,

electrode_voltages

    The electrode voltages to be used for defining the bias window for the current calculation. If no voltage is specified it will use the voltages in the self-consistent calculation. If voltages are specified the current will be obtained non-self-consistent.

    Type: Must be given as 2 voltages - for example, [-0.5, 0.5]*Volt.
    Default: If no electrode voltages are specified the same voltages will be used as those set on the calculator for the electronic structure calculation

yes i understand that bias voltage used to identify bias window, but my question is, if i use electrode voltage from 0 to 2 this mean bias window from 0 to 2 also??
from my information , bias window is chemical potential of left and right electrode??

Thanks in Advance
Khattab   

22

General Questions and Answers / Re: Bias window identifcation help

« on: November 4, 2014, 22:30 »

Dear Dr Anders Blom,
Thank you very much for your answer, but could you till me how to calculate bias widow for any bias voltage for example, 1, 2 or 3
Regards,
Khattab

23

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

24

General Questions and Answers / Re: Dos interpretation help!!!

« on: September 28, 2014, 11:09 »

Dear Dr Anders Blom,
Thank you very much for answer .
Regards,
El-Sayed Khattab

25

General Questions and Answers / Re: Dos interpretation help!!!

« on: September 25, 2014, 15:45 »

Dear Zh,
Thank you very much for your answer , I want to study electron transport through some organic molecules, the objective of my question is to guide me to some papers help me to understand what is DOS and how to interprete its curves.
Thank you again,
El-Sayed Khattab     

26

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 

27

General Questions and Answers / Re: Relaxation problem

« on: July 9, 2014, 16:18 »

Dear Dr Anderson,
Thank you very much 
Kind Regards,
Khattab

28

General Questions and Answers / Re: Relaxation problem

« on: July 9, 2014, 12:36 »

Dear Dr Anderson,
Firstly,thank you very much for your detailed replay, also thank you very much for you time. finally thank you very much for you attention to help me to overcome my obstacle .
Now i relaxed one molecule and it normally terminated, i carried out relaxation process with Single Zeta basis set for all molecules, i want to calculate current by double zeta polarized, when i run the jop, the process terminated abnormally and give me this error message

Traceback (most recent call last):
  File "c:/users/elbanna/appdata/local/temp/tmpwqvkl-.nl", line 651, in ?
    runtime_parameters = runtime_parameters
NLValueError: One of or more atoms has a different number of orbitals.
Terminated Abnormally

when i run calculation with Single zeta i don't get this error message, now i want to calculated current with double zeta polarized basis set if this available  How can i do this 
Kind Regards,
Sayed 

29

General Questions and Answers / Re: Relaxation problem

« on: July 6, 2014, 01:03 »

Dear Dr Anderson,
Firstly, thank you for you answer , my molecule is 22 atom, what i mean by relaxation is to  relax the molecule between two electrodes before calculating current.
Note :- the molecule is already optimized separately by gaussian 09.
Best Regards,
Khattab

30

General Questions and Answers / Re: Relaxation problem

« on: July 2, 2014, 11:22 »

Dear All,
I want to study trend between series of some molecules, but relaxation process is very slowly and high time consuming , i tried to decrease basis set, the calculation be faster but i don't got the relaxed structure till now, how can i solve this problem, my supervisor need this results as soon as possible, i don't make any thing, What can i do Can any help me to overcome this obstacle 
Waiting For Help !!!!!
Kind regards,
Khattab