Titlebook: Aspects of Many-Body Effects in Molecules and Extended Systems; Proceedings of the W D. Mukherjee Conference proceedings 1989 Springer-Verl

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Separability Problem in General Many Electron Systems CI calculation will obviously restore the symmetry, but since that is neither practicable nor desirable, additional conditions are imposed to ensure that the resultant functions are symmetry-adapted even at the trial function level.

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Quantum Chemistry in Fock Space of electrons is fixed. So Fock space is, in a sense, a direct sum of Hilbert spaces for various particle numbers. Processes like ionization or electron attachment, in which the number of electrons is changed are hence better described in Fock space than in configuration space (i.e. in . particle Hilbert space).

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Quantum Chemistry in Fock Space particles) or in Fock space (where operators act on the occupation numbers of spin orbitals). The representation of operators in Fock space (often also referred to as occupation number representation or 2. quantization) is essentially equivalent to the representation in configuration space, it is,

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Size Extensivity Correction for CI Energies Based on Complete Active Space Reference Functionsctrons in the system. This so called “size extensivity” (SE) problem causes truncated CI energies (e.g., those which include all excitations up through some specified level) energies to be of questionable value, for example, in computing thermodynamic energy differences such as chemical reaction ene

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