On the mutual exclusion of variationality and size consistency

So Hirata, Ireneusz Grabowski

Research output: Contribution to journalArticlepeer-review


Why do variational electron-correlation methods such as truncated configuration-interaction methods tend to be non-size-consistent (non-size-extensive)? Why are size-consistent (size-extensive) methods such as Møller- Plesset perturbation and coupled-cluster methods nonvariational? We conjecture that the variational and sizeconsistent properties are mutually exclusive in an ab initio electron-correlation method (which thus excludes the Hartree-Fock and density-functional methods). We analyze some key examples that support the truth of this conjecture.

Original languageEnglish (US)
Article number1440
Pages (from-to)1-9
Number of pages9
JournalTheoretical Chemistry Accounts
Issue number3
StatePublished - Mar 2014


  • Configuration-interaction theory
  • Coupled-cluster theory
  • Diagrams
  • Electron correlation
  • Møller-plesset perturbation theory
  • Size consistency
  • Size extensivity
  • Variational principle

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry


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