Author Topic: HOMO & LUMO Idetification from MPSH energy spectrum (Read 6921 times)

Khattab · « **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

Umberto Martinez · « **Reply #1 on:** December 11, 2014, 08:36 »

HOMO-1 and LUMO+1 refers to the second highest and second lowest orbital, respectively.
In your case:
...
18 HOMO-2
19 HOMO-1
20 HOMO
21 LUMO
22 LUMO+1
23 LUMO+2
...

Khattab · « **Reply #2 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

Anders Blom · « **Reply #3 on:** December 12, 2014, 02:22 »

That is not possible since the output only contains the eigenvalues and not the occupations of the levels.

Khattab · « **Reply #4 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

Umberto Martinez · « **Reply #5 on:** December 15, 2014, 13:19 »

This is true if your zero energy reference is the Fermi level.
You should get the occupation printed in your MolecularEnergy spectrum analysis log.
Check also the examples here http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.molecularenergyspectrum.html

Khattab · « **Reply #6 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

Anders Blom · « **Reply #7 on:** December 16, 2014, 03:43 »

If you do nlprint() on an MPSH spectrum, the occupations will also be reported (at least in any recent ATK version).

Khattab · « **Reply #8 on:** December 16, 2014, 10:24 »

Dear Dr Anders blom,
Thank you for your replay, i checked my version and i don't find this option, i use ATK 2008.10 version is this option is available

If not could you help me to overcome this obstacles

because i writing my paper now and i want to use this data

Thanks in advance,
Khattab

Anders Blom · « **Reply #9 on:** December 16, 2014, 16:19 »

That version is not supported any more. You can try to look in the reference manual for your version and compare to http://quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.molecularenergyspectrum.html and see if you can use a similar solution as in the newer version (the code at the bottom).

Khattab · « **Reply #10 on:** December 17, 2014, 16:47 »

Dear Dr Anders blom,
Thank you very much for your replay and your support for me not only for this question but in many previous question and posts,
Now i searched my manual and, i found that my script have nlprint option as the following
######################################################################
# Calculate physical properties
######################################################################
projected_hamiltonian_energy_spectrum = calculateProjectedHamiltonianEnergySpectrum(
self_consistent_calculation = scf,
projection_atoms = (18,19,20,21,22,23,24,25,26,27,28,29,)
)
if processIsMaster(): nlPrint(projected_hamiltonian_energy_spectrum)
if processIsMaster(): file.addToSample(projected_hamiltonian_energy_spectrum, 'Test22', 'Projected Hamiltonian Energy Spectrum')

I recalculate MPSH Energy spectrum and project it on the molecule atoms only and i got different results as in the attached files, Now is this right

The script i used ( also attached ) can print the occupation

Now can i specify the energy of HOMO, LUMO, LUMO+1 and so on

Thanks in Advance,
Khattab

Khattab · « **Reply #11 on:** December 29, 2014, 08:17 »

Urgently need help

Dear All,
please help me as soon as possible, i carried out some calculation on series of system which matched on its structures with benzen-1,4-dithiol, i calculate energy spectrum and i want to identify HOMO, HOMO-1, HOMO-2, LUMO, LUMO+1 and LUMO +2 as so on, the attached file (compressed) here is the input and out put of my system ( BDT) as an example, form the log file how can i identify these orbitals

Waiting for help as soon as possible

Thanks in advance
Khattab

Khattab · « **Reply #12 on:** December 30, 2014, 13:20 »

Quote from: Khattab on December 29, 2014, 08:17

Urgently need help
Dear All,
please help me as soon as possible, i carried out some calculation on series of system which matched on its structures with benzen-1,4-dithiol, i calculate energy spectrum and i want to identify HOMO, HOMO-1, HOMO-2, LUMO, LUMO+1 and LUMO +2 as so on, the attached file (compressed) here is the input and out put of my system ( BDT) as an example, form the log file how can i identify these orbitals

Waiting for help as soon as possible
Thanks in advance
Khattab

Please help me

Khattab · « **Reply #13 on:** December 31, 2014, 11:59 »

Quote from: Anders Blom on December 12, 2014, 02:22

That is not possible since the output only contains the eigenvalues and not the occupations of the levels.

Dear Dr Anders blom,
The attached file here is the log file of MPSH energy spectrum with population information, could you tell me know, which orbital is HOMO and which is lumo

Thanks in Advance,
Khattab

Anders Blom · « **Reply #14 on:** January 4, 2015, 00:01 »

The Mulliken populations have nothing to do with the energy level occupations.

Formally there is no HOMO or LUMO level in a device with open boundary conditions, since there is no Fermi level in the middle of the device, but one can compare the shape of the eigenstates between the isolated molecule and the molecule in the device to make the connection.

A natural suspicion is that HOMO is the level closest to the Fermi level (with negative energy).

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