Spin contamination

{
  "id": "MLC-T-CHM-011198",
  "term": "Spin contamination",
  "field": "Chemistry",
  "definition": "The mixing of different spin states in a quantum mechanical wavefunction that is intended to represent a pure spin state. This phenomenon arises in approximate quantum chemical calculations, particularly when using unrestricted Hartree-Fock methods for open-shell systems. It can lead to inaccuracies in calculated energies and properties.",
  "subject": "Organic and Biomolecular Chemistry",
  "see_also": [
    "hartree",
    "contamination",
    "spin projection"
  ],
  "references": [
    "PAC, 1999, 71, 1919. 'Glossary of terms used in theoretical organic chemistry' on page 1962 (https://doi.org/10.1351/pac199971101919)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/spin-contamination/"
}