Theory

This section contains a brief introduction to Koopmans functionals.

• Quasiparticle energies, piecewise linearity, and Koopmans’ theorem
• Koopmans functionals
  • The motivating idea behind the functionals
  • Derivation of the functionals
  • Understanding the functional
• The key ingredients in a Koopmans calculation
  • The variational orbitals
  • The screening parameters
    • ΔSCF
    • DFPT
    • Computational scaling for periodic systems
  • The flavour: KI or KIPZ
    • KI
    • KIPZ
• The Koopmans workflows
• Limitations
  • Issues with metals
• Related methods

For more details, refer to our various publications.