An international group of scientists has subjected to sulfur dioxide high pressure and could observe a reversible transition of the molecular amorphous state in the polymer amorphous. At pressures around 26 GPA in a wide temperature range from 77 to 300 Kelvin sulfur molecules coordinated around the three atoms of oxygen, forming a disordered polymer chain. The results of a study published in the journal Proceedings of the National Academy of Sciences.
The ability of a substance to exist in several different amorphous modifications called polyamorphism. Similarly, polymorphism in transparent crystals it is characterized by the presence of a substance of two or more forms of disordered (or amorphous, or liquid), which would be different in structure, but preserve the stoichiometry (ratio of atoms). Often this phenomenon is accompanied by changes in the number of coordinated atoms and the density of the material. Transitions between amorphous States occur under the influence of temperature and pressure, but, in contrast to crystalline polymorphs, structural transitions of amorphous systems are performed smoothly due to the lack of periodicity of the crystal structure.
Significant structural transitions, leading to the amorphization observed under pressure, molecular crystals, which have multiple bonds. Under pressure and at low temperatures they can rupture and form between neighboring molecules, forming polymer chains. Scientists have already observed a similar behavior of such molecules as nitrogen, carbon dioxide and benzene.
Sulfur dioxide plays an important role in many industrial, atmospheric and geological processes. Unlike the molecules of CO2, the Central atom which forms two double bonds, SO molecule2 is curved and described by two resonance structures with one single and one double bond. Huachao Zhang (Zhang Huichao) with colleagues from University of science and technology of China in Hefei have studied the behavior of this substance under conditions of extremely high pressures up to 60 GPA in a wide temperature range from 77 to 300 Kelvin. Gas are condensed and subjected to pressure cell with diamond anvils, and the changes were followed using Raman spectroscopy and x-ray diffraction.