Hi Remya,

FIrst you need to know the overall charge and oxidation state of your Fe-centers (like +2 or +3). Then if you replace one Fe atom with a Na atom (neutral) there must be a residual negative charge in your system.

Since you are asking about the overall charge for the input file, Fe12O12 is neutral, so it is reasonable to assume that the Fe atoms are in the +2 state (on average). You replace one with Na, which can only be in the +1 state. So you will be left with [Fe11O12Na]-. The input charge is -1. Your spin state will depend on the initial spin state which, in turn, depends on the geometry. See Article Competition between surface chemisorption and cage formation...

Dear Remya,

to determine the charge of Fe₁₂O₁₂ and the effect of replacing one Fe atom with Na, we have to consider the oxidation states of the elements involved:

1. Fe₁₂O₁₂ Charge Calculation:

*Iron commonly exists in oxidation states +2 and +3.

*Oxygen on the other side in oxides is typically -2.

For Fe₁₂O₁₂, assuming Fe is in the +3 oxidation state, which is common in iron oxides like Fe₂O₃ for instance:

12 x (+3) + 12 x (-2) = 36 - 24 = +12

**Replacing One Fe with Na>>>

Na typically exists as +1 (Na⁺).

If we replace one Fe³⁺ with Na⁺, the total charge changes as follows:

(+12) - (+3) + (+1) = +10

So, in your Gaussian calculation, the system Fe₁₁O₁₂Na should be assigned a total charge of +10.

Consequently, replacing Fe³⁺ with Na⁺ in Fe₁₂O₁₂ to form Fe₁₁O₁₂Na reduces the charge from +12 to +10, leading to:

*Electronic changes: Possible Fe³⁺ → Fe²⁺ reduction, altering magnetic/electronic properties.

*Structural distortion - Na⁺ (larger than Fe³⁺) may cause local lattice strain.

*Magnetic disruption - Fe-Fe interactions change, possibly affecting magnetism.

*Chemical instability - Charge imbalance may increase reactivity.

*Computational adjustments - Gaussian input needs +10 charge and correct spin multiplicity.

Thank you al for the answers