Secular Equation

*c _{i}|F-ε_{i}S|c_{i}
= 0*

c_{i}: eigenvector; *F*: Fock matrix; *
ε> _{i}*: eigenvalue;

in which *P*: density matrix; *H*: one-electron matrix. The general Fock Matrix element is

*F _{μν}^{α} = H_{μν}
+*Σ

Or, spin-free

*F _{μν} = H_{μν}
+*Σ

The methods all use a minimum basis set consisting of a maximum of one atomic orbital for each angular quantum number. The normal basis set for any atom consists of one *s* and three *p* orbitals (*p _{x}*,