RESUMEN

Here we investigate the structural properties of the Mn0.9Co0.1NiGe half-Heusler alloys under pressure up to 12 GPa by Synchrotron angle-dispersive x-ray diffraction (XRD). At room temperature and pressure, the compound exhibits only the hexagonal NiIn2-type structure. Lowering the temperature to 100 K at ambient pressure induces an almost complete martensitic phase transformation to the orthorhombic TiNiSi-type structure. With increasing pressure, the stable orthorhombic phase gradually undergoes a reverse martensitic transformation. The hexagonal phase reaches 85% of the sample when applying 12 GPa of pressure atT= 100 K. We further evaluated the bulk modulus of both hexagonal and orthorhombic phases and found similar values (123.1 ± 5.9 GPa for hexagonal and 102.8 ± 4.2 GPa for orthorhombic). Also, we show that the lattice contraction induced is anisotropic. Moreover, the high-pressure hexagonal phase shows a volumetric thermal contraction coefficientαv∼ -8.9(1) × 10-5K-1when temperature increases from 100 to 160 K, evidencing a significant negative thermal expansion (NTE) effect. Overall, our results demonstrate that the reverse martensitic transition presented on Mn0.9Co0.1NiGe induced either by pressure or temperature is related to the anisotropic contraction of the crystalline arrangement, which should also play a crucial role in driving the magnetic phase transitions in this system.

RESUMEN

Nonlinear optical materials have been investigated recently due to their potential technological applications in information storage and communications. In this context, semi-organic crystals can effectively combine the desired nonlinear optical properties of amino acids with the promising mechanical and thermal properties of inorganic materials. In this work, we have synthesized and characterized a semi-organic crystal of the amino acid L-histidine and hydrofluoric acid and investigated the chemical interactions between the organic and inorganic moieties. The crystal of L-histidine bis(fluoride) has been produced by slow solvent evaporation and characterized by X-ray diffraction (XRD) crystallography and thermogravimetric and differential thermal analyses. The XRD conducted using the Rietveld method shows that the unit cell is orthorhombic with the P21212 space group and contains four L-histidine bis(fluoride) units. Both differential thermal analysis and temperature-dependent XRD show that the crystals are thermally stable up to 191°C and do not undergo phase transition. The computational Hirshfeld surface analysis of the crystal structure reveals the main intermolecular interactions. Density functional theory has been employed to calculate the ionic interaction energy and electrostatic potential maps and confirm the spontaneity of ionic association at 191°C. The combined experimental and computational results show that the thermal stability of the semi-organic L-histidine bis(fluoride) crystal makes it suitable for nonlinear optical applications in optical sensing and communication systems.

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RESUMEN

A cocrystal of glibenclamide, an antidiabetic drug classified as type II compound according to the Biopharmaceutics Classification System, has been synthesized using tromethamine as coformer in 1:1 molar ratio, by slow solvent evaporation cocrystalization. The cocrystal obtained was characterized by X-ray powder diffraction, differential scanning calorimetry, Raman, mid infrared, and near-infrared spectroscopy. The results consistently show the formation of a cocrystal between active pharmaceutical ingredients and conformer with the synthons corresponding to hydrogen bonding between hydrogen in amines of tromethamine and carbonyl and sulfonyl groups in glibenclamide.

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