ORNL Scientists Unveil Promethium’s Hidden Features, Paving Way for Lanthanide Research

Scientists at the Department of Energy’s Oak Ridge National Laboratory (ORNL) and the National Institute of Standards and Technology have discovered new features of the elusive element promethium. Using a combination of experimentation and computer simulation, they purified the promethium radionuclide and synthesized a coordination complex for the first time. The team used the IBM AC922 supercomputer Summit to model the element. Promethium, one of 15 lanthanides or rare earth elements, is used in modern technology such as electric motors, spacecraft batteries, radiation therapy, smartphones, and computer monitors.

Unraveling the Mysteries of Promethium

Promethium, the elusive 61st element on the periodic table, has been a subject of intrigue since its discovery in 1945 at the Department of Energy’s Oak Ridge National Laboratory (ORNL). Despite being part of the lanthanide series, promethium’s exact chemical nature remained largely unknown until recently. A team of scientists from ORNL and the National Institute of Standards and Technology has now successfully synthesized and characterized a coordination complex of promethium, shedding light on its chemical properties. Their findings were published in the scientific journal, Nature.

The Lanthanide Series and Promethium’s Role

The lanthanide series comprises 15 elements, including promethium, often referred to as rare earth elements. Despite their name, these elements are not rare and are extensively used in modern technology, from electric motors and spacecraft batteries to smartphones and computer monitors. Promethium, however, has remained elusive due to its radioactive nature and short half-life of only 2 ½ years. This has made it challenging for scientists to characterize its bound form, which is crucial for understanding an element’s electronic structure and properties.

The Experimental Investigation of Promethium

The team’s investigation of promethium involved developing a novel, water-soluble complexing agent and using X-ray absorption spectroscopy to determine the element’s electronic structure. However, experimental methods alone could not provide a complete picture of promethium’s properties. To overcome this, the team combined experimental techniques with theoretical and computational chemistry, using the IBM AC922 supercomputer Summit at the Oak Ridge Leadership Computing Facility at ORNL. This approach allowed them to simulate promethium’s electronic structure, providing a more comprehensive understanding of the element.

The Challenges of Simulating Promethium’s Electronic Structure

Simulating promethium’s electronic structure was not without its challenges. It required solving complex equations to model the element’s electrons, which behave more like waves than particles in fixed orbits around the nucleus. The key to this simulation was solving the Schrödinger equation, which describes the wavefunctions and energies of electrons in an atom or molecule. This information, combined with observations from spectroscopy, allowed the scientists to represent promethium in 3D, providing a more detailed picture than could be achieved through experimentation alone.

The Significance of the Findings

The successful characterization of promethium’s coordination complex marks a significant milestone in our understanding of the lanthanide series. It not only fills a longstanding gap in our knowledge of these elements but also opens up new avenues for research into other lanthanides. The team’s approach, combining experimental and computational methods, demonstrates the power of interdisciplinary research in advancing our understanding of the natural world. As Dmytro Bykov, a theoretical chemist at ORNL, aptly put it, “We all stand on the shoulders of giants… And it all came together to characterize and fully understand this remarkable compound of this very rare element for the first time.”