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Sub-system self-consistency in coupled cluster theory.

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This summary is machine-generated.

Coupled-cluster (CC) energies can be calculated differently by diagonalizing effective Hamiltonians. This method works even for sub-systems of a single electron, offering new approaches for quantum chemistry calculations.

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Area of Science:

  • Quantum Chemistry
  • Computational Physics
  • Many-Body Theory

Background:

  • Coupled-cluster (CC) theory is a standard method for calculating the electronic structure of atoms and molecules.
  • The standard calculation of CC energies involves a complex iterative process based on the CC ansatz.

Purpose of the Study:

  • To explore alternative methods for calculating single-reference coupled-cluster (CC) energies.
  • To demonstrate the feasibility of reconstructing CC energies through the diagonalization of effective Hamiltonians.

Main Methods:

  • Numerical evidence was provided for alternative CC energy calculations.
  • The study focused on diagonalizing effective Hamiltonians for correlated sub-systems.
  • The extreme case of a single-electron sub-system was investigated.

Main Results:

  • CC energies can be calculated by diagonalizing effective Hamiltonians, deviating from the copybook definition.
  • Reconstruction of CC energy was achieved by diagonalizing effective Hamiltonians of correlated sub-systems.
  • The CC energy was reproduced by diagonalizing the effective Hamiltonian of a single-electron sub-system.

Conclusions:

  • The properties of the CC formalism allow for novel computational protocols.
  • Effective interactions in sub-systems can be defined as probes for calculating total system energy.
  • A new type of self-consistency for approximate CC approaches can be introduced.