Structural investigation of three distinct amorphous forms of Ar hydrate

Three amorphous forms of Ar clathrate hydrate (pressure-amorphized, annealed and recovered) were characterized by isotope substitution (36Ar) neutron diffraction and molecular dynamics and their local coordinations analyzed and compared to pure ice.

Polymorphism of pharmaceuticals

Chapter 7 deals with polymorphism in pharmaceuticals. Following a discussion of the problem of determining the statistics of the occurrence of polymorphism in pharmaceuticals, I present a discussion and examples of the connection between polymorphism and the rate of dissolution and solubility, bioavailability, and the importance of phase changes and mixtures of forms in pharmaceutical preparations. I survey some of the considerations and techniques involved in screening for crystal forms: solvent selection, specific screening for solvates and hydrates, gel crystallization, crystallization in ionic liquids, the challenge of difficult to obtain stable forms and unstable new forms, and the outlook on new techniques and conditions for crystallization. The chapter also deals with polymorphism in pharmaceutical co-crystals, excipients, and amorphous forms and the importance and utility of chemical microscopy in the study of polymorphism of pharmaceuticals.

Pressure-induced amorphization and existence of molecular and polymeric amorphous forms in dense SO2

We report here the pressure-induced amorphization and reversible structural transformation between two amorphous forms of SO2: molecular amorphous and polymeric amorphous, with the transition found at 26 GPa over a broad temperature regime, 77 K to 300 K. The transformation was observed by both Raman spectroscopy and X-ray diffraction in a diamond anvil cell. The results were corroborated by ab initio molecular dynamics simulations, where both forward and reverse transitions were detected, opening a window to detailed analysis of the respective local structures. The high-pressure polymeric amorphous form was found to consist mainly of disordered polymeric chains made of three-coordinated sulfur atoms connected via oxygen atoms, with few residual intact molecules. This study provides an example of polyamorphism in a system consisting of simple molecules with multiple bonds.

CONTRIBUTION TO THE KNOWLEDGE OF THE MAGNESITE DEPOSITS IN BOSNIA AND HERZEGOVINA

Magnesite is an industrial mineral of magnesium, which most often occurs in the form of crystalline, massive and amorphous forms. Mineral magnesite has a wide and varied application in the production of high-strength materials: powder (flour), sinter, bricks (magnesite, magnesite-chromite, forsteric, etc.). In the construction industry it is used for the production of magnesium cement. In smaller quantities it is used in chemical, pharmaceutical, rubber and other industrial branches. The area of the so-called "Bosnian Serpentine Zone" are stand out in the area of the inner Dinarides of Bosnia and Herzegovina, among numerous phenomena and larger deposits of magnesite. In terms of quality, the variability from high quality to those that can not be used in the refractory industry is determined. Magnesite deposits mostly require certain preparation procedures in order to achieve higher quality magnesite. The paper presents deposits and the appearance of magnesite in Bosnia and Herzegovina, with emphasis on the results of previous research, quality, reserves, usability and laboratory testing, and the results of the latest X - ray examinations from one site have been presented.