To scientists at Oak Ridge National Laboratory (ORNL) It has been possible to discover previously hidden properties of one of the rare earth elements, promethium. This opens the way for broader applications in many different fields, from medicine to space travel. Discovered 80 years ago at ORNL, lanthanide is produced in small quantities and used in medical research and atomic batteries. However, we still know very little about him. It is difficult to know anything about an element that does not have stable isotopes and its quantity in the entire Earth’s crust at any given time does not exceed half a kilogram.
Researchers intended Promethium complex, thanks to which it became possible to study the properties of this element in solution for the first time. Promethium has no stable isotopes, so it was the last of the lanthanides to be discovered and the most difficult to study.“, says Ilya Popovs of ORNL. Lanthanides are elements with atomic numbers from 57 to 71. The atomic number of promethium is 61. Lanthanides have similar chemical properties but differ in size.
The remaining fourteen lanthanides, excluding promethium, are well known. These minerals have interesting properties that make them indispensable in modern technologies. We use them in lasers, permanent magnets in wind turbines, electric cars, devices that emit X-rays and in cancer treatment. Thousands of scientific articles have been published on the chemistry of lanthanides. However, it does not include promethium. This is a clear gap in our knowledge. Scientists have to guess most of its properties. Now we can finally explore some of them“, says co-author Santa Janson Popova.
For the purposes of the study, the researchers produced a small amount of bromethium 147, which has a half-life of 2.62 years. They obtained an element of sufficient purity to study its properties. The team of scientists performed the first demonstration of the shrinkage phenomenon for an entire series of lanthanides in solution. Lanthanides have a similar electronic structure, giving them similar physical and chemical properties. However, as the charge of the nucleus increases, contraction occurs, i.e. the atomic and ionic radii decrease, thanks to which they acquire unique properties.
ORNL researchers can now also study this phenomenon for promethium to better determine the shape of the contraction trend across the lanthanide series. Scientifically, it was amazing. I was immediately blown away when we got all the data. The contraction of chemical bonds is constantly accelerating, but after promethium it slows down significantly. This is a very important contribution to understanding how lanthanides form chemical bonds and describing structural changes in the periodic table.Adds Alex Ivanov.
This discovery will, among other things, facilitate the separation of elements from each other. In modern technologies we cannot use a mixture of lanthanides. First, you need to separate the individual elements from each other. This is why shrinkage is so important. It allows us to separate isotopes, which is a very difficult task“, explain the scientists.
Many modern devices were used in the research, including the Summit supercomputer, which was used to perform calculations in the field of quantum chemistry and molecular dynamics. Summit is the ninth most powerful supercomputer in the world. ORNL also owns Frontier, the world’s most powerful supercomputer. The authors of the Promethium paper hope that in the future they will be able to perform their calculations on the frontier.
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