In the first approxiation if you perform a molecular orbital calculation on a molecule, you will get a series of meolcular oribatl energies. If you have a singlet state originally (paired electrons) the HOMO-LUMO energy (the lowest energy transition) can be directly calculated as a difference between the HOMO and LUMO orbitals. It can be converted into wave number or wavelength. Higher energy transitions can also be calculated as orbital energy differences. The intensity of the transitions may be estimated by transition dipole moment calculations using the orbitals . but that should be programmed. Semiempirical calculations usually do not give too reliable UV-VIS spectra, but there are programs paramterized to give reliable results.

http://basic.ub.ac.id/web/sites/default/files/eproceeding2013/Chemistry/PSC20.pdf

http://arxiv.org/ftp/arxiv/papers/1105/1105.3766.pdf

http://www.chalcogen.ro/Migalska.pdf

http://msc.psu.edu/tutorials/Intro_CompChem.pdf

Please find attached some references which may be of some help

If your molecule is still secret prior publication, please give the kind of molecule (p.e. conjugated fluorochrome, aromatic annelated or no-annelated......) .

You can read and contact Jens (Res.Gate member) according to :

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Thesis: Prediction of UV-VIS Absorbance Data for Polycyclic Aromatic Hydrocarbons (PAHs). Performance of the LCOAO Procedure for Medium to Large Benzenoid Chromophores

Kasper Høyrup, Jens Spanget-Larsen

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This paper is very interesting and perhaps helpful for you.

Another questions related to your molecule:

- Have you an experimental spectrum?

- Do you want to obtain a spectrum with transitions as vertical strokes (old manner) or a spectrum showing gaussian/lorentz shapes like an experimental spectrum?

JRG

i have the experimental data of the sample, which is in absorbance mode. I wish to match the theoretical and experimental results. I will consult you further after reading the paper sent by you. I have tried to get the spectrum using Zindo-Cl method and has measured mullikan charge and dipole strength for each transition. by taking the help of the software but still i am unable to convert the data into the spectrum as i am unable to know that for plotting the uv-vis graph of the spectrum which property i have to consider against energy

UV VIS spectra consist of fairly broad bands because of the intermolecular interactions and because of the vibrational fine structure. Therefore you may correlate the calculated energy difference between the molecular oritals and the wavenumber of the maximum of the absorption peak

http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htm

This may be a rough approximation as the 0-0 transition is usually at somewhat higher frequency:

http://131.104.156.23/Lectures/CHEM_207/uv-vis.htm

http://www.phys.ubbcluj.ro/~dana.maniu/OS/BS_7.pdf

At low temperature and in thre gas state the fine structure can be resolved better.

The basics you are providing are known to me. I am interested in finding the spectrum theoretically. not by comparing the experimental data to the data provided in the books. I want to calculate the spectrum by applying Zindo calculations. and want to learn the basics of zindo.

b initio calculation of UV-Vis absorption spectra of a

single molecule chlorophyll a: Comparison study between

RHF/CIS, TDDFT, and semi-empirical methods

1* Veinardi Suendo & 2 Sparisoma Viridi

1Inorganic and Physical Chemistry Research Division, Department of Chemistry,

Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung,

Jalan Ganesha 10, Bandung 40132, Jawa Barat, Indonesia

2 Nuclear Physics and Biophysics Research Division, Department of Physics, Faculty of

Mathematics and Natural Sciences, Institut Teknologi Bandung,

Jalan Ganesha 10, Bandung 40132, Jawa Barat, Indonesia

*Corresponding author. Tel.: +62 222502103, Fax: +62 222504154, email:

[email protected]

Abstract. Chlorophyll a is one the most abundant pigment on Earth that

responsible for trapping the light energy to perform photosynthesis in green

plants. This molecule is a metal-complex that consists of a porphyrin ring with

high symmetry that acts as ligands with magnesium as the central ion.

Chlorophyll a has been studied for many years from different point of views for

both experimental and theoretical interests. In this study, the restricted Hartree-

Fock configuration interaction single (RHF/CIS), time-dependent density

functional theory (TDDFT) and some semi-empirical methods (CNDO/s and

ZINDO) calculations were carried out and compared to reconstruct the UV-Vis

absorption spectra of chlorophyll a. In some extend, the calculation results based

on a single molecule calculation were succeeded to reconstruct the absorption

spectra but required to be scaling to match the experimental one. Different

computational methods (ab initio and semi-empirical) exhibit the differences in

the energy correction factor and the presence of transition states, however, still

conserve the main spectral features. In general, the semi-empirical methods

provide a better energy scaling factor, which means closer to the experimental

one. However, they lack of fine features or vertical transitions with respect to the

experimental spectra. The ab initio calculations result more complete features

than the semi-empirical methods, especially the TDDFT with high level of basis

sets that provides a good accuracy in transition energies. The contribution of

ground states and excited states orbitals in the main vertical transitions is

discussed based on orbital structure. This might gives a new perspective to

explain the energy transfer phenomena in the absorption processes that related to

the function of chlorophyll a as a light-harvesting antenna.

http://arxiv.org/ftp/arxiv/papers/1105/1105.3766.pdf

Dear Sangeeta,

please read my answer to Ilze and the pdf joined to my answer.

- concerning your last answer and your wish to learn the basics of Zindo and later ZINDO /S (CI).

Please order the references of Zerner (1973 and 1991) et al through your librarian and obtain the program of Zerner et al.

If not avaible at this time , Here you can see the basics of ZINDO/S in the books of the following software.

References:

J. Ridley, M. Zerner, Theor. Chim. Acta 1973, 32, 111 – 134.

Jump up ^ M. Zerner, Reviews in Computational Chemistry, Volume 2, Eds. K. B. Lipkowitz and D. B. Boyd, VCH, New York, 313, (1991

The original program from the Zerner group is not widely available but the method is implemented in HyperChem, in part, in Gaussian, and in SCIGRESS

XXXXXXXXXXXXXXXXX

Dear Ilze,

I need some infos concerning your question.

- what a Hyperchem version are you using?

- Have you the books belonging to the software? If yes, you can read the pages 127, 151 and 295 to 297 and the cited references concerning ZINDO/S.

- When you compute UV-Vis spectra with Hyperchem , you should do a C.I. singles calculation at first.

- What a kind of molecule are you investigating? This is important for a correct answer.

- You must spend a lot of time and read the published references concerning your molecule and the belonging transitions.

- Please note that Hyperchem´s implementation of Zindo/S is restricted to spin multiplicities up to a quartet state. Higher spin systems may not be done using Hyperchem (After Hyperchem /Supported methods).

Please note that a computer needs more, more time when you perform your calculations with Hyperchem. The use of Mopac (see Stewart reference

http://openmopac.net/manual/ ) and the algorithms in Mopac work and give faster calculations results than Hyperchem.

Useful links:

http://openmopac.net/param_manual/strategies.html

http://winmostar.com/en/manual_en/calcmanual_en.html

JRG

XXXXXXXXXXXXXXXXXXXXXX

I hope you can find a little help with my answer.

Good luck

JRG

Here the pdf.

Investigating CAChe for use in freshman chemistry courses: Comparison of various computational methods in the determination of partial charge, dipole moments, and bond order and UV-Vis.

i have gone through the first pdf you have send me. It was the one of the first few papers I have gone through, I am willing to know how he has got the spectrum from the data provided by the software. i have gone through a paper in which the authors have plotted the energy vs the oscillator strength. i follow the same but i found that the experimental and the theoretical spectrum of the molecule does not match with each other. secondly the theoretical spectrum is very tedious one.

i am working with polymers and to calculate the theoretical UV-Vis spectrum I am using arguslab

There are lots of methods to obtain UV-Vis spectrum. such as TDDFT, ZINDO, CIS(D), CASSSCF, CASSPT2 and EOD-CCSD etc. You can choice one of them.

But you need to remember that some methods cannot be used to calculate UV-Vis for polymer molecule due to the system size.

If the total atom numbers is not over 250, you can use TDDFT or CIS calculation.

The basic principle of UV-vis spectrum is Frank-Condon principle which can easily found in google search. Briefly, No structural change is not allowed during the transition from to ground to excited state (only for absorption!!!)

I've searched arguslab program in google. The simple calculations can be performed . In this program, only way to calculate uv-vis spectrum is ZINDO.

I installed this program in my personal computer but i cannot perform ZINDO.

The detail basic theory of ZINDO, you can find in google. Briefly, the basic of ZINDO hamiltonian is based on the INDO. Both method are semi-empirical which implies that the specific parameters need to set up for calculation of molcule. It is too hard to tell you about all of basic theory of ZINDO. I recommend you should search on web.

I just give a comment about processing of ZINDO calculation in arguslab program. In calculation tab, you can find UV-Vis. If you activate UV-Vis spectrum, you can see the ZINDO electronic spectra calculation window. Please choice ZINDO-CI method and set up singlet. After that you can click the start button. If you are interested more than 10 excited state(default), you can control the number. This is the simply way to calculate UV-Vis spectrum in arguslab program.

If you have any question, please let me know

Hope this help

I've read your answer. OMG, you already know how to perform.

There is no option for drawing spectra.

To drawing spectra, you need to use matlab or gnuplot or origin programs.

You also need to give gaussian broadening for matching exp and theo

I also recommend you to perform UV-vis calculation using many excited state.

Hope this help

Please use; Ab initio calculation of UV-Vis absorption spectra of a single molecule chlorophyll a: Comparison study between RHF/CIS, TDDFT, and semi-empirical methods

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&ved=0CCsQFjAA&url=http%3A%2F%2Farxiv.org%2Fpdf%2F1105.3766&ei=xUAjU7esKMaC4gT26oHoAw&usg=AFQjCNGbCTgugEWnlJd-_uVvsraDEj2w9w

please ujval if can help let me know

I have run the calculations and whatsoever is written above. these are relevant answers to my question. I just wish to know what I have to do with the data I obtain from the calculations I got by running the program.

Which software have you used for calculations? Its important to know to suggest the way how to plot spectra...

Please try using Gaussian 98 system 

sir I can not spend money to buy the software so using the free softwares.

Respected Jeremiah Odhek Masime sir i have read the Ab initio calculation of UV-Vis absorption spectra of a single molecule chlorophyll a: Comparison study between RHF/CIS, TDDFT, and semi-empirical methods

  I dont understand how this correction factor is caluclated please explain if possible

I am getting theoretical Uv spectra from GAussian09 w using TD DFT method.But sir what about the scaling factor ?