Orthonormal basis

It is often computationally convenient to use an orthonormal basis. This is constructed from the CSBAS basis by a Lowdin orthogonalization procedure. The resulting symmetry-adapted orthonormal basis is denoted low.

The MOs are computed by diagonalization of the Fock matrix in the LOW representation. The resulting eigenvectors are easily transformed back to any other representation whenever suitable, such as for instance to the primitive cartesian bas representation (including the CFs).