search

psi4 / psi4numpy

Combining Psi4 and Numpy for education and development.
BSD 3-Clause "New" or "Revised" License
330 stars 151 forks source link

Additional term in making matrix elements of similarily transformed hamiltonian #122

Closed DavidGoing closed 1 year ago

DavidGoing commented 2 years ago

In the code of making matrix elements of similarily transformed hamiltonian(coupled cluster/RHF/helper_cchbar). image The notes tell that these term only differ by one sign. However, additional term appears in build_Hovvo, making the hamiltonian no longer antisymmetric. image I am wondering what happened and why this term is needed.

lothian commented 2 years ago

In a spin-adapted RHF formalism, these two terms are distinct. Antisymmetry of the integrals and HBAR matrix elements only applies in a spin-orbital formulation.