Zr-oxide secondary building units construct metal–organic framework (MOF) materials with excellent gas adsorption properties and high mechanical, thermal, and chemical stability. These attributes have led Zr-oxide MOFs to be well-recognized for a wide range of applications, including gas storage and separation, catalysis, as well as healthcare domain. Here, we report structure search methods within the Cambridge Structural Database (CSD) to create a curated subset of 102 Zr-oxide MOFs synthesized to date, bringing a unique record for all researchers working in this area. For the identified structures, we manually corrected the proton topology of hydroxyl and water molecules on the Zr-oxide nodes and characterized their textural properties, Brunauer–Emmett–Teller (BET) area, and topology. Importantly, we performed systematic periodic density functional theory (DFT) calculations comparing 25 different combinations of basis sets and functionals to calculate framework partial atomic charges for use in gas adsorption simulations. Through experimental verification of CO2 adsorption in selected Zr-oxide MOFs, we demonstrate the sensitivity of CO2 adsorption predictions at the Henry’s regime to the choice of the DFT method for partial charge calculations. We characterized Zr-MOFs for their CO2 adsorption performance via high-throughput grand canonical Monte Carlo (GCMC) simulations and revealed how the chemistry of the Zr-oxide node could have a significant impact on CO2 uptake predictions. We found that the maximum CO2 uptake is obtained for structures with the heat of adsorption values >25 kJ/mol and the largest cavity diameters of ca. 6–7 Å. Finally, we introduced augmented reality (AR) visualizations as a means to bring adsorption phenomena alive in porous adsorbents and to dynamically explore gas adsorption sites in MOFs.
The anharmonicity of O–H stretching vibrations of water ice is characterized by use of a periodic implementation of the vibrational self-consistent field (VSCF) and vibrational configuration interaction (VCI) methods, which take phonon–phonon couplings explicitly into account through numerical evaluation of high-order terms of the nuclear potential. The low-temperature, proton-ordered phase of water ice (namely, ice XI) is investigated. The net effect of a coupled anharmonic treatment of stretching modes is not just a rigid blue-shift of the respective harmonic spectral frequencies but rather a complex change of their relative spectral positions, which cannot be captured by simple scaling strategies based on harmonic calculations. The adopted techniques allow for a hierarchical treatment of anharmonic terms of the nuclear potential, which is key to an effective identification of leading factors. We show that the anharmonic independent-mode approximationonly describing the “intrinsic anharmonicity” of the O−H stretchesis unable to capture the correct physics, and that couplings among O−H stretches must be described. Inspection of harmonic normal coordinates allows identification of specific features of the O–H stretching motions which most likely enable strong mode–mode couplings. Finally, by coupling O–H stretches to all other possible modes of ice XI (THz collective vibrations, molecular librations, bendings), we identify specific types of motion which significantly affect O–H stretching states: in particular, molecular librations are found to affect the stretching states more than molecular bendings.
The anharmonicity of O-H stretching vibrations of water ice is characterized by use of a periodic implementation of the vibrational self-consistent field (VSCF) and vibrational configuration interaction (VCI) methods, which take phonon-phonon couplings explicitly into account through numerical evaluation of high-order terms of the nuclear potential. The low-temperature, proton-ordered phase of water ice (namely, ice-XI) is investigated. The net effect of a coupled anharmonic treatment of stretching modes is not just a rigid blue-shift of the respective harmonic spectral frequencies but rather a complex change of their relative spectral positions, which can not be captured by simple scaling strategies based on harmonic calculations. The adopted techniques allow for a hierarchical treatment of anharmonic terms of the nuclear potential, which is key to an effective identification of leading factors. We show that an anharmonic independent-mode approximation only describing the "intrinsic anharmonicity" of the O-H stretches is unable to capture the correct physics and that couplings among O-H stretches must be described. Inspection of harmonic normal coordinates allows to identify specific features of the O-H stretching motions which most likely enable strong mode-mode couplings. Finally, by coupling O-H stretches to all other possible modes of ice-XI (THz collective vibrations, molecular librations, bendings), we identify specific types of motion which significantly affect O-H stretching states: in particular, molecular librations are found to affect the stretching states more than molecular bendings.
Some Grenville-age rocks exposed in the uplifted region of the Hudson Highlands of southern New York are amphibole-dominant igneous rocks. The amphibole-rich rocks, which are locally pegmatitic in nature, are associated with magnetite ore and coarse-grained syenite; the ore was discovered and mined from the middle of the 18th century to the end of the 19th century. The amphiboles have attracted the attention of many researchers for nearly two centuries. Chemical analyses demonstrate that they are pargasite or hastingsite in composition and are particularly rich in Cl and K. High-precision crystal structure analyses of 11 Cl-rich amphiboles from the Hudson Highlands (0.0134 <R1 < 0.0169), including separation of M(1)Fe and M(1)Mg, allow corroboration of, and greatly extends the range of, previous models of Cl incorporation in amphiboles that were derived from a small number of samples. In addition to crystal structures and major-element analyses, trace-element data and Raman spectra are provided.
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