Учёные из России и Германии открыли «невозможное» соединение золота
Учёные из России открыли «невозможное» соединение золота
Translation
Scientists from Russia and Germany discovered the "impossible" connection of gold
Scientists from Russia and Germany discovered the secret of the stability of calaverite, a strange and rare mineral of gold, and found evidence that this noble metal can form an extremely unusual compound with tellurium.
Their findings and calculations were presented in the journal PNAS.
"The mineral calaverite has an amazing destiny. Noticeably affecting the "gold rush", it has been a headache and a great paradox for crystallographers for many decades. The deeper it was studied, the more new questions arose.
Our team managed to connect all the oddities of calaverite within a simple model, and experimenters can now hunt for the new compound predicted by us," says Artem Oganov, Professor Skoltech and MIPT.
Gold, unlike most other metals, has a high chemical inertness and is practically not found in nature in the form of large deposits of various compounds with other elements.
Most of the gold reserves mined by mankind before the beginning of the 20th century were found in the form of nuggets and pure deposits of this metal.
The only exception to this rule is the mineral calaverite, a compound of gold and tellurium, AuTe2. He has long been interested not only in gold miners, but also chemists and physicists, as calaverite has an extremely unusual structure, which can not be explained in the framework of the classical doctrine of the structure of crystals.
Only relatively recently, scientists have solved the mystery of his device, describing it in four-dimensional space.
This description, as noted by Oganov and his colleagues, gave rise to a new problem — gold in such crystals will have an "incorrect" oxidation state — +2, which will make them unstable in terms of chemistry. Russian scientists and their German colleagues have found out why calaverite still exists, using the USPEX system created by Oganov a few years ago to predict the properties of chemical elements and crystals.
To do this, scientists first had to think about how to calculate the properties of such a complex compound. They found a way out of this situation, using another natural mineral of gold — silvanite, its connection with tellurium and silver, as a kind of "template" for calculating the properties of individual parts of calaverite.
Having calculated the properties of silvanite and replacing silver atoms with gold, Oganov and his team found out that calaverite does not consist of gold oxidized to the degree of +2, but a mixture of atoms in two different oxidation States — +1 and +3, distributed over the crystal in a special way.
"To place monovalent and trivalent gold, even if it existed, so that they are equally repeated in each direction, on the triangular lattice of calaverite is simply impossible. Therefore, nature is forced to compromise-smoothly change the valence of gold in the crystal.
The environment of tellurium reacts to this, which leads to unusual distortions of the crystal lattice," explains Sergey Streltsov from the Institute of metal physics of RAS in Yekaterinburg.
The same calculations, as noted by scientists, revealed several interesting and unusual properties of calaverite. In particular, it was found that it can be converted into a superconductor by compressing to ultra-high pressures or adding atoms of platinum and some other metals. Such behavior, according to chemists, is not typical for gold compounds.
In addition, the calculations of Oganov and his colleagues show that there may be another "impossible" compound of gold and tellurium, AuTe. As the chemist suggests, it will also have an unusual structure and interesting properties, including superconductivity.
Учёные из России открыли «невозможное» соединение золота
Translation
Scientists from Russia and Germany discovered the "impossible" connection of gold
Scientists from Russia and Germany discovered the secret of the stability of calaverite, a strange and rare mineral of gold, and found evidence that this noble metal can form an extremely unusual compound with tellurium.
Their findings and calculations were presented in the journal PNAS.
"The mineral calaverite has an amazing destiny. Noticeably affecting the "gold rush", it has been a headache and a great paradox for crystallographers for many decades. The deeper it was studied, the more new questions arose.
Our team managed to connect all the oddities of calaverite within a simple model, and experimenters can now hunt for the new compound predicted by us," says Artem Oganov, Professor Skoltech and MIPT.
Gold, unlike most other metals, has a high chemical inertness and is practically not found in nature in the form of large deposits of various compounds with other elements.
Most of the gold reserves mined by mankind before the beginning of the 20th century were found in the form of nuggets and pure deposits of this metal.
The only exception to this rule is the mineral calaverite, a compound of gold and tellurium, AuTe2. He has long been interested not only in gold miners, but also chemists and physicists, as calaverite has an extremely unusual structure, which can not be explained in the framework of the classical doctrine of the structure of crystals.
Only relatively recently, scientists have solved the mystery of his device, describing it in four-dimensional space.
This description, as noted by Oganov and his colleagues, gave rise to a new problem — gold in such crystals will have an "incorrect" oxidation state — +2, which will make them unstable in terms of chemistry. Russian scientists and their German colleagues have found out why calaverite still exists, using the USPEX system created by Oganov a few years ago to predict the properties of chemical elements and crystals.
To do this, scientists first had to think about how to calculate the properties of such a complex compound. They found a way out of this situation, using another natural mineral of gold — silvanite, its connection with tellurium and silver, as a kind of "template" for calculating the properties of individual parts of calaverite.
Having calculated the properties of silvanite and replacing silver atoms with gold, Oganov and his team found out that calaverite does not consist of gold oxidized to the degree of +2, but a mixture of atoms in two different oxidation States — +1 and +3, distributed over the crystal in a special way.
"To place monovalent and trivalent gold, even if it existed, so that they are equally repeated in each direction, on the triangular lattice of calaverite is simply impossible. Therefore, nature is forced to compromise-smoothly change the valence of gold in the crystal.
The environment of tellurium reacts to this, which leads to unusual distortions of the crystal lattice," explains Sergey Streltsov from the Institute of metal physics of RAS in Yekaterinburg.
The same calculations, as noted by scientists, revealed several interesting and unusual properties of calaverite. In particular, it was found that it can be converted into a superconductor by compressing to ultra-high pressures or adding atoms of platinum and some other metals. Such behavior, according to chemists, is not typical for gold compounds.
In addition, the calculations of Oganov and his colleagues show that there may be another "impossible" compound of gold and tellurium, AuTe. As the chemist suggests, it will also have an unusual structure and interesting properties, including superconductivity.