xbasen). Inserting Eq. (16.6) into Eq. (16.2) a matrix equation is easily obtained for the coefficient cp . Actually, not all the coefficients cp are independent each other as there are other two conditions to be satisfied: the HOMO condition, see Eq. (16.4), and the charge condition
|cpgp()d = - 1 ,||(16.7)|
Note that for the computation of the final KS Hamiltonian, only orbital basis-set matrix elements of vxEXX are required, which can be easily computes as three-index Coulomb integrals. Thus the present OEP-EXX implementation is grid-free, like Hartree-Fock, but in contrast to all other XC-functionals.