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It is a special case of the configuration interaction method in which all Slater determinants (or configuration state functions, CSFs) of the proper symmetry are included in the variational procedure (i.e., all Slater determinants obtained by exciting all possible electrons to all possible virtual orbitals, orbitals which are unoccupied in the electronic ground state configuration).
Configuration interaction (CI) is a post-Hartree–Fock linear variational method for solving the nonrelativistic Schrödinger equation within the Born–Oppenheimer approximation for a quantum chemical multi-electron system. Mathematically, configuration simply describes the linear combination of Slater determinants used for the
Python-based Simulations of Chemistry Framework (PySCF) is an ab initio computational chemistry program natively implemented in Python program language. [ 1 ] [ 2 ] The package aims to provide a simple, light-weight and efficient platform for quantum chemistry code developing and calculation.
Multi-configurational self-consistent field (MCSCF) is a method in quantum chemistry used to generate qualitatively correct reference states of molecules in cases where Hartree–Fock and density functional theory are not adequate (e.g., for molecular ground states which are quasi-degenerate with low-lying excited states or in bond-breaking situations).
In quantum chemistry, n-electron valence state perturbation theory (NEVPT) is a perturbative treatment applicable to multireference CASCI-type wavefunctions.It can be considered as a generalization of the well-known second-order Møller–Plesset perturbation theory to multireference complete active space cases.
This requires a wavefunction that includes a set of electronic configurations with high and very similar importance. Dynamic correlation , representing the contribution to the energy brought by the instantaneous interaction between electrons, is normally small and can be recovered with good accuracy by means of perturbative evaluations, such as ...
Secretary of State Marco Rubio has directed the State Department to freeze applications in the passport pipeline with “X” selected as the gender identifier, according to internal communication ...
Penguin diagram: a quark changes flavor via a W or Z loop Tadpole diagram: One loop diagram with one external leg Self-interaction or oyster diagram An electron emits and reabsorbs a photon Box diagram The box diagram for kaon oscillations: Photon-photon scattering: Higgs boson production: Via gluons and top quarks: Via quarks and W or Z bosons ...