Lagrange multipliers molecular structure

We have presented a practical Hartree-Fock theory of atomic and molecular electronic structure for individual electronically excited states that does not involve the use of off-diagonal Lagrange multipliers. An easily implemented method for taking the orthogonality constraints into account (tocia) has been used to impose the orthogonality of the Hartree-Fock excited state wave function of interest to states of lower energy. 

Since time-independent KS theory is commonly used in calculations of molecular structures and properties, we will focus on this form of the theory. We will briefly return to the time-dependent formalism later. The KS Lagrange multipliers in Eqs. [82] and [83] reflect the response of the total electronic energy to changes in occupation number (n/f), i.e.,... 

---