Introduction to Coupled Cluster theory

These notes have been prepared in October 2018 for a two hour lecture on coupled cluster theory in the context of the course of Prof. Ursula Röthlisberger entitled Introduction to Electronic Structure Methods at EPFL, Lausanne, Switzerland.

See References for the content I used to write these notes and look also at the List of abbreviations if needed.

Feel free to re-use this documentation for academic purposes and Contact me if you have any question or comment.

Sections

• 1. Let’s Recap
• 2. What is Coupled Cluster Theory?
• 3. Size-consistency, size-extensivity, and strict separability
  • 3.1. Size-consistency
  • 3.2. Size-extensivity
  • 3.3. Strict separability
  • 3.4. Why do we want size-extensivity?
• 4. The Coupled Cluster equations
  • 4.1. The exponential ansatz
  • 4.2. The CC Schrödinger equation
  • 4.3. The CC amplitudes
• 5. CC models and comments
  • 5.1. Standard CC models
  • 5.2. Computational cost
  • 5.3. What is CC theory used for?

Appendices

• CI and CC for the hydrogen dimer
• List of abbreviations
• References
• Contact