## Hartree-Fock algorithm

The Hartree-Fock equations are, in their simplest form, solved in an iterative way, starting with a guess for the coefficients $$C_{i\alpha}$$. We label the coefficients as $$C_{i\alpha}^{(n)}$$, where the subscript $$n$$ stands for iteration $$n$$. To set up the algorithm we can proceed as follows:

• We start with a guess $$C_{i\alpha}^{(0)}=\delta_{i,\alpha}$$. Alternatively, we could have used random starting values as long as the vectors are normalized. Another possibility is to give states below the Fermi level a larger weight.
• The Hartree-Fock matrix simplifies then to (assuming that the coefficients $$C_{i\alpha}$$ are real)
$$\hat{h}_{\alpha\beta}^{HF}=\epsilon_{\alpha}\delta_{\alpha,\beta}+ \sum_{j = 1}^A\sum_{\gamma\delta} C_{j\gamma}^{(0)}C_{j\delta}^{(0)}\langle \alpha\gamma|\hat{v}|\beta\delta\rangle_{AS}.$$