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The Fock operator for a closed system is given by

f = H(core) + sum (2*f - k)

where f is the Coulomb operator and k is the exchange operator. The summation goes from 1 to N/2. My questions is why is the summation to N/2 and why does one have to multiply the Coulomb operator by 2?

Thanks in advance

Best regards

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# Homework Help: Fock operator for closed shell system

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