Aaron J Celestian

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Neutron powder diffraction data were collected on a sample of natrolite and a 1:1 (v/v) mixture of perdeuterated methanol and water at a pressure of 1.87(11) GPa. The natrolite sample was superhydrated, with a water content double that observed at ambient pressure. All of the water deuterium atoms were located and the nature and extent of the hydrogen(More)
Combining information from time-resolved X-ray and neutron scattering with theoretical calculations has revealed the elegant mechanism whereby hydrogen crystalline silicotitanate (H-CST; H2Ti2SiO7 x 1.5 H2O) achieves its remarkable ion-exchange selectivity for cesium. Rather than a simple ion-for-ion displacement reaction into favorable sites, which has(More)
Glaciers in the tropical Andes have been rapidly losing mass since the 1970s. In addition to the documented increase in temperature, increases in light-absorbing particles deposited on glaciers could be contributing to the observed glacier loss. Here we report on measurements of lightabsorbing particles sampled from glaciers during three surveys in the(More)
The crystal structure of the selective Cs+ ion exchanger D1.6H0.4Ti2SiO7.D2.66H0.34O1.5, known as crystalline silicotitanate or CST, has been determined in both native (D-CST) and in the Cs+-exchanged forms ((Cs, D)-CST) from angle-dispersive and time-of-flight neutron diffraction studies. The final fully exchange Cs+ form transformed from D-CST with unit(More)
The title compound, lithium potassium dialuminium digermanium octaoxide dihydrate, (K,Li)-(Al,Ge)-GIS (GIS is gismondine), is the result of a 50% Li(+) exchange into the K-(Al,Ge)-GIS structure. The (K,Li)-(Al,Ge)-GIS structure was determined from a 4 x 4 x 2 micro m octahedral single crystal at the ESRF synchrotron X-ray source. The ion exchange results in(More)
We report on the synthesis and structure of tribasic lead maleate hemihydrate ([Pb4O3]C2H2(CO2)2.(1/2)H2O, TRIMAL) and lead maleate (PbC2H2(CO2)2, PBMAL). The structure of [Pb4O3]C2H2(CO2)2.(1/2)H2O, solved ab initio from X-ray powder diffraction data, consists of infinite slabs of edge-sharing OPb4 tetrahedra, of composition [Pb4O3], running along the c(More)
A Nb-substituted titanium silicate with the sitinakite (NbTS) topology was exchanged with Sr(2+) to determine the mechanisms and pathways of ion diffusion through this mixed polyhedral nanoporous framework. The refined structural models yield unit cell parameters and atomic positions of Sr(2+) and suggest that there was a two-step process during cation(More)
The exchange of Cs(+) into H(1.22)K(0.84)ZrSi(3)O(9)·2.16H(2)O (umbite-(HK)) was followed in situ using time-resolved X-ray diffraction at the National Synchrotron Light Source. The umbite framework (space group P2(1)/c with cell dimensions of a = 7.2814(3) Å, b = 10.4201(4) Å, c = 13.4529(7) Å, and β = 90.53(1)°) consists of wollastonite-like silicate(More)
In our ongoing investigations of heteropolyniobate chemistry, a phase featuring decorated, A-type trivacant alpha-Keggin ions linked by their charge-balancing sodium cations has been isolated and structurally characterized. This is the first heteropolyniobate reported that has a true lacunary structure type. Na15[(PO2)3PNb9O34] x 22 H2O (1) [triclinic space(More)
A new potassium gallosilicate zeolite with a natrolite topology (approximate formula K8.2Ga8.2Si11.8O40.11.5H2O) was synthesized under hydrothermal conditions and characterized as a function of temperature using monochromatic synchrotron X-ray powder diffraction and Rietveld analyses. Unlike the previously known tetragonal K8Ga8Si12O40.6H2O phase, the(More)