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$$ 
U\left(R,r,s\right) =  E_{NN} \left( R \right) + E_{Ne} \left( {R,r,s} \right) + E_{ee} \left( {r,s} \right) + E_{KE} \left( {r,s} \right) + E_{PR} \left( { \uparrow  \downarrow ,S} \right)
$$

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