Heat capacities and thermodynamics of formation of flat-Al13 nitrate - [Al13(OH)24(H2O)24](NO3)15·11H2O

Dana Reusser, Jacob Schliesser, William S. Elliott, Brian F. Woodfield, Darren W. Johnson, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Abstract We report enthalpies of formation from the elements and oxides, Δf = -(26195.31 ± 34.46) kJ · mol-1 and Δf,oxH = -(1402.09 ± 33.36) kJ · mol-1, for crystalline [Al133-OH)62-OH)18(H2O)24](NO3)15·11H2O(cr) (flat-Al13) measured using aqueous solution room temperature calorimetry. This material is a nitrate salt of a polynuclear aluminum hydroxide ion with thirteen aluminum metal centers, Al1315+. Unlike the ε-Al137+ Keggin ion, it contains solely octahedrally coordinated aluminum in a more flat topology. We also report heat capacities from temperatures of (2 to 300) K on this flat-Al13 nitrate using a Quantum Design Physical Property Measurement System (PPMS). These measurements were used to calculate the standard molar entropy and subsequently the free energy of formation for this material. We observed that during the heat capacity measurements, the flat-Al13 sample underwent a second order phase transition near T = 214 K.

Original languageEnglish (US)
Article number4296
Pages (from-to)224-231
Number of pages8
JournalJournal of Chemical Thermodynamics
Volume90
DOIs
StatePublished - Jul 22 2015
Externally publishedYes

Keywords

  • Enthalpy of formation
  • Flat Al
  • Heat capacity
  • Keggin ion
  • Polyoxocation

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)
  • Physical and Theoretical Chemistry

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