In this work, the polymorphism of octadecanoic acid (C₁₈H₃₆O₂, stearic acid) was studied as a function of organic solvent polarity.

Context: Ammonium Tutton salts have been widely studied in recent years due to their thermostructural properties, which make them promising compounds for application in thermochemical energy storage devices. In this work, a detailed experimental study of the Tutton salt with the formula (NH₄)₂Zn(SO₄)₂(H₂O)₆ is carried out. Its structural, vibrational, and thermal properties are analyzed and discussed. Powder X-ray diffraction (PXRD) studies confirm that the compound crystallizes in a structure of a Tutton salt, with monoclinic symmetry and P2₁/a space group. The Hirshfeld surface analysis results indicate that the main contacts stabilizing the material crystal lattice are H···O/O···H, H···H, and O···O. In addition, a typical behavior of an insulating material is confirmed based on the electronic bandgap calculated from the band structure and experimental absorption coefficient. The Raman and infrared spectra calculated using DFT are in a good agreement with the respective experimental spectroscopic results. Thermal analysis in the range from 300 to 773 K reveals one exothermic and several endothermic events that are investigated using PXRD measurements as a function of temperature. With increasing temperature, two new structural phases are identified, one of which is resolved using the Le Bail method. Our findings suggest that the salt (NH₄)₂Zn(SO₄)₂(H₂O)₆ is a promising thermochemical material suitable for the development of heat storage systems, due to its low dehydration temperature (≈ 330 K), high enthalpy of dehydration (122.43 kJ/mol of H₂O), and hydration after 24 h. Methods: Computational studies using Hirshfeld surfaces and void analysis are conducted to identify and quantify the intermolecular contacts occurring in the crystal structure. Furthermore, geometry optimization calculations are performed based on density functional theory (DFT) using the PBE functional and norm-conserving pseudopotentials implemented in the Cambridge Serial Total Energy Package (CASTEP). The primitive unit cell optimization was conducted using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm. The electronic properties of band structure and density of states, and vibrational modes of the optimized crystal lattice are calculated and analyzed. Graphical

In this research, we investigated the influence of Mn²⁺ ions on the packing in stearic acid (SA) crystals through the use of Raman spectroscopy, X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The crystals investigated were obtained utilizing the slow evaporation methodology in a hexane solution under varying manganese (Mn) concentrations sourced from MnSO₄ 5H₂O (0.5, 1.0, 1.5, 2.0, 4.0, and 6.0%). XRD studies indicated that all SA crystals were grown in the B_m form (monoclinic), favoring the gauche conformation in molecular packing. Additionally, crystalline lattice modifications were observed through Raman spectral changes in the low-vibrational energy region. Variations in the intensities and Raman shifts in two lattice vibrational modes, centered at approximately 59 and 70 cm⁻¹, revealed that two types of hydrogen bonds are distinctly affected within the crystalline lattice. Furthermore, the unit cell parameters (a, b, c, and β) were determined via Rietveld refinement, and their behavior was analyzed as a function of Mn concentration. The results indicated that Mn²⁺ ions exert a strain and deformation effect on the unit cell. Lastly, differential scanning calorimetry (DSC) was employed to evaluate the thermal stability of the B_m form of SA crystals.

This work will present a new crystal of KH2PO4 (KDP) modified with the palladium ions derived from palladium-II (PdCl2), at concentrations of 0.5 % and 1.0 %, with the intention of investigating the potential changes caused by the presence of Pd ions in the crystal lattice of KDP. The crystals were grown by the slow evaporation method and characterized by different techniques, including Raman Spectroscopy from room temperature to 630 K, infrared (IR), thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction (XRD). All the techniques used demonstrated sensitivity to detect different changes depending on the sample concentration. The results were analysed by comparing the data from the pure crystal and the doped crystals. The shift and changes in the Raman bands, due to the incorporation of palladium atoms in the lattice, are analysed in the pure KDP and, in Pd-doped crystals. Changes in crystal melting, monoclinic phase shift, and the emergence of previously unreported Raman bands are analysed and discussed. Additionally, computational simulations were performed on the crystal structure using Density Functional Theory (DFT) to evaluate the effect of Pd doping on electronic structures, and band gap. The results are very interesting, as they demonstrate that the KDP crystal lattice effectively accommodates palladium ions in its structure, presenting new physical characteristics.