Structural and thermodynamic effects of hydration in Na-zeolite A (LTA) from low-temperature heat capacity

Matthew S. Dickson, Spencer G. Shumway, Grace Neilsen, Alexandra Navrotsky, Brian F. Woodfield

Research output: Contribution to journalArticlepeer-review


Zeolite A (Linde Type A; LTA) is an industrially important porous mineral that has recently been shown to exhibit framework flexibility upon changes in hydration level. To investigate the flexibility transition from a thermodynamic perspective, we have performed heat capacity measurements on sodium zeolite A at seven incremental hydration levels ranging from zero to equilibrium with ambient air. Excess low-frequency vibrations beyond the predictions of the Debye model are found in all samples, and the frequency of these vibrations increases as a function of hydration level. This suggests that an increase in hydration causes a decrease in at least one type of framework flexibility for sodium zeolite A. In addition, a subtle excess heat capacity contribution from 150 to 280 K is observed only for low and intermediate hydration levels, which may arise from a transformation tied to framework flexibility previously observed in zeolite A via gas absorption calorimetry. Values of the standard thermodynamic functions Cp,m°, Δ0TSm°, Δ0THm°, and Φm° are also reported.

Original languageEnglish (US)
Article number107023
JournalJournal of Chemical Thermodynamics
StatePublished - Jun 2023


  • Boson peak
  • Flexibility
  • Heat capacity
  • Hydration
  • LTA
  • Zeolite A

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • General Materials Science
  • Physical and Theoretical Chemistry


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