During their annual expedition to Kamchatka, a group of scientists from St Petersburg University discovered a new mineral – dokuchaevite. It is named after Vasily Dokuchaev, a distinguished scientist of the 19th century and the founder of soil science. The composition and crystal structure of the new mineral species have no close analogues not only among known minerals, but also among synthetic compounds.
Since 2014, a research team supervised by Oleg Siidra, Professor at St Petersburg University, has been studying fumaroles of Kamchatka volcanoes. ‘Fumaroles on scoria cones formed as a result of past eruptions of Tolbachik volcano have a unique mineralogical diversity. By now, more than 400 of the 5,500 known minerals have been found there. We can say that the fumaroles of Tolbachik Volcano are a kind of a rainforest of the Amazonian inorganic world. About 15% of all the minerals of the planet are concentrated here!’ said Oleg Siidra, head of the research team.
Like most minerals of the Tolbachik Volcano fumaroles, where the new mineral was found, dokuchaevite (Cu8O2(VO4)3Cl3) has a unique crystal structure and composition. It has no analogues among natural or synthetic compounds. Studies of the new mineral crystals have been carried out by Evgeny Nazarchuk, Associate Professor at St Petersburg University, using the equipment of the Resource Centre for X-Ray Diffraction Studies at the Research Park of St Petersburg University. They showed that copper atoms are surrounded by oxygen and chlorine in the structure of dokuchaevite. The number of diverse variants of such combinations was not previously fixed in any known mineral. The St Petersburg University researchers also found oxocentered tetrahedral complexes with copper in the structure of the new mineral.
‘The presence in the structure of such fragments formed by magnetic copper ions makes it possible to consider this mineral, as well as some other fumarolic minerals, as a potential source of interesting magnetic materials with various practical applications. The oxocentered tetrahedron OCu4 is a simple frustrated complex since it consists of four spin triangles. At the two vertices of each triangle, the spins are identified in their direction, but at the third one they are not,’ said Oleg Siidra.
The search for potential materials demonstrating the properties of quantum spin liquids is a highly relevant task in modern solid-state physics. It is believed that in the near future such materials will find application in the creation of quantum computers.
Oleg Siidra, Professor at St Petersburg University
According to the results of crystal chemical analysis and for the possibility of manifestation of certain physical properties, a synthesis of pure analogues is carried out. They are used to study properties with the potential applications in materials science and industry. This approach of the team, supervised by Professor Oleg Siidra, differs from others in Russia and in the world by the full cycle of all the research carried out in the context of the ‘From Minerals to Materials’ strategy. To study physical features of dokuchaevite, the scientists synthesised its analogue, simulating the processes of mineral formation from gas in fumaroles.
‘With the help of the laboratory of the Department of Crystallography and equipment of the Resource Centre for Diagnostics of Functional Materials for Medicine, Pharmacology and Nanoelectronics of the St Petersburg University Research Park, Viktoria Vladimirova, a master’s student at St Petersburg University, managed to obtain and study a pure sample of yaroshevskite. It is distantly related to dokuchaevite in composition and was discovered seven years ago. However, nobody managed to synthesize it in the laboratory. The study of synthetic material showed that its magnetic substructure turned out to be one of the most complex for all frustrated magnetic materials known to date. Additionally, we observed a number of interesting phenomena. To understand them, more detailed investigations are needed,’ emphasised Oleg Siidra, Professor at St Petersburg University.
The research project to discover dokuchaevite, and to study its properties and synthetic analogues is supported by a grant from the Russian Foundation for Basic Research.