3
$\begingroup$

In Frank Jensen's Introduction to Computational Chemistry ($\mathrm{2^{nd}}$ edition), on page 99, it says:

For an ROHF wave function, it is not possible to choose a unitary transformation that makes the matrix of Lagrange multipliers in eq. (3.41) diagonal, and orbital energies from an ROHF (Restricted Open-shell Hartree–Fock) wave function are consequently not uniquely defined and cannot be equated to ionization potentials by a Koopmans-type argument.

Here ROHF eq. (3.41) is the non canonical Hartree-Fock equation:

$$F_i\phi_i=\sum\lambda_{ij}\phi_j$$

But in ATTILA SZABO, NEIL S. OSTLUND's Modern Quantum Chemestry, they prove that the Hartree-Fock equation can always be put into the canonical form:

$$F_i\phi_i=\lambda_{i}\phi_i$$

What am I misunderstanding here?

$\endgroup$
  • 1
    $\begingroup$ I'm guessing that "restricted open-shell" part is important. $\endgroup$ – Buck Thorn Mar 5 at 10:56
  • $\begingroup$ ATTILA SZABO, NEIL S. OSTLUND showed that there is a basis where the hartree-fock equation has the form $F_i\phi_i=\lambda_{i}\phi_i$ that is, it does not work for every basis , only for a kind special of basis , so there is no issue in the two statements $\endgroup$ – amilton moreira Mar 5 at 12:50

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.