How to find the ligand field splitting of d orbitals in a square planar complex?

I am working with a Iron square planar complex with $\ce{NH2-}$ and $\ce{OH-}$ ligands having cis and trans conformation. My question is how to theoretically/computationally calculate the ligand filed splitting of the orbitals of Fe specifically?




I'm not an expert in this field yet, but I think Using Orca you can calculate the orbital energy numerically. I have used CASSCF as method of calculation.
The input file I've prepared is as following



```
! def2-TZVPP SlowConv PAtom
! Allpop
! printMOs
! PAl2


%casscf
    nel     6        #Numeber of electrons
    norb    5        #Number of Orbitals in active space
    mult    1,3,5    #Multiplicities (I've got this from Term symbols)
    nroots  11,11,5  #Number of micro states for each Multiplicity 
end



*xyz -2 5
    Fe       0.0000000000      0.0000000000      0.0000000000                 
    O        1.8600000000      0.0000000000      0.0000000000                 
    O       -1.8600000000      0.0000000000      0.0000000000                 
    N        0.0000000000      1.9400000000      0.0000000000                 
    N        0.0000000000     -1.9400000000      0.0000000000                 
    H       -0.8407460951      2.2854839793      0.5145942634                 
    H        0.8414809543      2.2855771457      0.5133281192                 
    H        2.1097954426      0.0911972135     -0.9540592676                 
    H       -2.1097621967      0.0917132162     -0.9538732789                 
    H        0.8411680767     -2.2854165305      0.5139464472                 
    H       -0.8411632857     -2.2854156190      0.5139547890                 
*

```

the xyz section has the coordination for atoms in your complex
and the CASSCF block contain the information about the active space
The output file has a section for orbital energy and occupation number of each orbital
For the bond length I've just searched on google for bond length of those atoms with Fe.


By analyzing the combination coefficients of orbitals, it is possible to obtain the energies required for these orbitals and subsequently calculate the splitting phenomenon. [![](https://i.stack.imgur.com/7tnrk.png)](https://i.stack.imgur.com/7tnrk.png)


By simply modifying the coordination in the input file, you can explore various configurations and calculate their corresponding properties. To achieve more accurate and reliable results, you may consider enhancing the basis set, which can lead to improved energy estimations


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