Correlated one-particle method: numerical results

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Computational physics

Background:

• A previous correlated one-particle method used a Fock operator and correlation potential.
• The goal was a correlated one-particle theory yielding all one-particle properties.
• Fock-space coupled-cluster method constructed infinite-order correlation potential for accurate ionization potentials (IPs) and electron affinities (EAs).

Purpose of the Study:

• To improve orbital choices in correlated one-particle theories.
• To introduce an effective Brueckner Hamiltonian by imposing the Brillouin-Brueckner condition.
• To assess the numerical properties of the effective Brueckner Hamiltonian.

Main Methods:

• Imposing the Brillouin-Brueckner condition to derive an effective Brueckner Hamiltonian.
• Approximating the effective Brueckner Hamiltonian through second-order perturbation theory.
• Calculating IPs, EAs, energies, and dipole moments using the developed method.

Main Results:

• The effective Brueckner Hamiltonian yields IPs and EAs correct through second order.
• Eigenfunctions of the Hamiltonian are second-order Brueckner orbitals.
• Expressions for energy and density matrix are provided, with results for sample molecules.

Conclusions:

• The developed method offers improved accuracy for calculating molecular properties.
• The Brillouin-Brueckner condition effectively enhances correlated one-particle theories.
• The study provides a robust framework for future theoretical chemistry research.