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06:42
Generation and Coherent Control of Pulsed Quantum Frequency Combs
Published on: June 8, 2018
Quadratic canonical transformation theory and higher order density matrices
Eric Neuscamman1, Takeshi Yanai, Garnet Kin-Lic Chan
1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14850, USA. eric.neuscamman@gmail.com
The Journal of Chemical Physics
|April 2, 2009
Summary
Canonical transformation (CT) theory offers accurate, efficient dynamic correlation for multireference systems. Enhancements improve accuracy for single and multireference cases, yielding competitive results with advanced methods.
Area of Science:
- Quantum chemistry
- Theoretical chemistry
- Computational chemistry
Background:
- Canonical transformation (CT) theory accurately describes dynamic correlation in multireference systems.
- Existing CT theory has limitations in single-reference scenarios compared to coupled cluster methods.
Purpose of the Study:
- To improve Canonical transformation (CT) theory for both single- and multireference systems.
- To investigate a quadratic commutator approximation and incorporate three-body reduced density matrices.
Main Methods:
- Developed a quadratic commutator approximation for the effective Hamiltonian.
- Integrated three-body reduced density matrices into operator and density matrix decompositions.
- Applied the enhanced CT theory to BH, HF, H2O, and N2 binding curves.
Main Results:
- The quadratic commutator approximation enhances CT accuracy for single-determinant references.
- Incorporating three-body information improves overall CT accuracy in multireference systems.
- CT calculations show results competitive with state-of-the-art methods like MRCI+Q and ACPF.
Conclusions:
- The enhanced CT theory provides a more accurate and versatile description of dynamic correlation.
- This advancement offers a cost-effective alternative to expensive high-level computational chemistry methods.
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