An Introduction to Configuration
Interaction Theory
C. David Sherrill
Center for Computational Quantum Chemistry, University
of Georgia
Contents
Introduction and Notation
Fundamental Concepts
Scope of the Method
Why Configuration Interaction?
The Correlation Energy
Slater's Rules
The Variational Theorem
The Method of Linear Variations
Variational Theorem for the Ground State
Why are Coupled-Cluster and MBPT Energies not Variational?
Application of the Variational Theorem to Other States
Convergence of the Wavefunction
Variational Theorem Bounds on Excited States
Reducing the Size of
the CI Space
Symmetry Restrictions on the CI Space
Classification of Basis Functions by Excitation Level
Energy Contributions of the Various Excitation Levels
Size of the CI Space as a Function of Excitation Level
The Frozen Core Approximation
Truncated CI is not Size Extensive
Second Quantization
Determinant-Based CI
Introduction to Determinant CI
Alpha and Beta Strings
Graphical Representation of Alpha and Beta Strings
Restricted Active Space CI
Olsen's Full CI Equations
Full CI Algorithm
References
Index
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