Dynamic disordering is the state of a crystal when influenced by temperature, rigid atomic groups begin to perform continuous rotations around their axis. Since borate crystals are obtained by crystallization fr om high-temperature melts, it is important for scientists and technologists to know whether any changes occur during the growing process because this can affect the quality of the resulting material. A team of scientists from Novosibirsk State University, the Sobolev Institute of Geology and Mineralogy SB RAS, and the Vereshchagin Institute for High Pressure Physics RAS conducted a targeted search for borate structures subject to dynamic disordering. As a result, they identified the first representative wh ere the possibility of this effect was demonstrated with quantum chemical modeling.
Pavel Gavryushkin, Candidate of Geological and Mineralogical Sciences and Associate Professor NSU Department of Geology and Geophysics, commented on the research,
Borates have a very wide spectrum of practical applications. For example, they are the main material for nonlinear optics that are used to convert the frequency of laser radiation. It is because of its practical significance for science and industry that almost three thousand representatives of borate structures have already been synthesized and are being studied in dozens of laboratories around the world. The discovery of new structural changes occurring in the high-temperature region for these compounds is an important research task. So, we decided to conduct a targeted study and find out whether the effects of dynamic disorder can manifest themselves for borate crystals.
The scientists conducted simulations using well-established methods of Ba3(BO3)2 crystal molecular dynamics and quantum chemistry and found a series of transitions in which the structure is gradually disordered. Specifically, [BO3] triangles gradually move from quasi-harmonic vibrations to continuous rotation around their axis. Interestingly, these transitions appear at relatively low temperatures with disordering recorded at 527 K, 1041 K, 1551 K, and 1748 K temperatures while the melting point is about 1640 K.
Research is published in the prestigious Physical Chemistry Chemical Physics (PCCP) journal.
