Hi Firoz, 

Gaussian and other software like ORCA are able to predict EPR spectra. You can read our publication about this technique: 10.1021/acs.inorgchem.6b00409 (I work with Vanadium(IV). 

Mr. Khan,

Please pay attention to:

http://www.gaussian.com/g_tech/g_ur/k_prop.htm

Thank you Giuseppe Sciortino for your comment. However, I wanted to know the specific keywords to be used in the input file for the calculations. The calculations for EPR can also be done by gaussian as told by Dr. Bojidarka B. Ivanova. Can you tell me a simple input file (for orca) which I can use to simulate EPR data for Vanadium(IV) ? Then I will try for Iron(III).

Dear Dr. Bojidarka B. Ivanova, I am highly obliged for your suggestion. I saw that gaussian page and I will try the same. Do you any papers where simulated EPR spectra has been reported through gaussian, specially for iron(III) systems?

Sure

Orca input:

#

# EPR of your complex

#

! UKS B2PLYP 6-311g(d,p) LargePrint TightSCF Grid5 SOMF(1X)

* xyz 0 2

Your coordinates

*

%eprnmr Nuclei = all V { aiso, adip, aorb }

gtensor 1 ewin -3,1000 ori -3

end

Obviously you need to change the charge and multiplicity and the functional and the basis set must be adequate to your metal. 

For some examples of gaussian input and output you can look the supplementary of the paper:

DOI: 10.1021/ed500794m