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

Abstract

a b s t r a c tWe report enthalpies of formation from the elements and oxides, D f H = À(26195.31 ± 34.46) kJ Á mol À1 and D f;ox H = À(1402.09 ± 33.36) kJ Á mol À1 , for crystalline [Al 13 (l 3 -OH) 6 (l 2 -OH) 18 (H 2 O) 24 ](NO 3 ) 15 Á 11H 2 O (cr) (flat-Al 13 ) measured using aqueous solution room temperature calorimetry. This material is a nitrate salt of a polynuclear aluminum hydroxide ion with thirteen aluminum metal centers, Al 13 15+ .Unlike the e-Al 13 7+ 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-Al 13 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-Al 13 sample underwent a second order phase transition near T = 214 K.

Systematic Study of Aluminum Nanoclusters and Anion Adsorbates

“…Another way to extend the work presented here is to compute the energetics and thermodynamics associated with the chemical reactions of Al nanoclusters, such as formation, dissociation, and cation exchange, which have been detailed in recent experimental studies. ,,, One approach to calculating these experimentally verifiable quantities is a first-principles thermodynamics analysis, which combines DFT-computed total energies and chemical potentials to map out the stability of different bulk and surface phases. , A more recent Hess’ law approach, developed by Rong and Kolpak, combines DFT total energies and tabulated Δ G SHE 0 values to form a Δ G expression that includes experimentally tunable parameters such as the concentration, pH, and applied potential.…”

Observation of alumina nanoparticles generated from aqueous solutions of a “flat” aluminum-13 cluster

“…It has been observed that the f-Al 13 cluster can break down in solution and reform into the e-Al 13 Keggin structure, and this process was hypothesized to be highly pH dependent. 24,25 The acid correction method forms solutions with slightly larger agglomerated species with a minute decrease to their PDI. This data may indicate that ripening is occurring via acid-digestion of metal oxide cluster side products, forming AlO x monomer units.…”