Term: zero-point energy
https://doi.org/10.1351/goldbook.08215

Definition:
Extent, in consequence of Heisenberg’s Uncertainty Principle, by which a particle or a set of particles has an energy greater than that of the minimum on the potential-energy surface.

Notes:
1) Because of zero-point energy, a molecular entity has a nonzero probability of adopting a geometry whose energy is greater than that of the energy minimum.
2) A molecular entity with zero-point energy may even adopt a geometry with a potential energy greater than its total energy, a possibility that permits tunnelling.
3) Because the magnitude of zero-point energy increases with decreasing mass, it is significant in the context of isotope effects, especially of hydrogen isotopes.

Source: PAC, 2022, 94, 353. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)' on page 525 (https://doi.org/10.1515/pac-2018-1010)

Citation: 'zero-point energy' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.08215

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