Thomas Albrecht-Schmitt is the Gregory R. Choppin Professor of Chemistry at Florida State University is the leader of an international research team that also includes Manfred Speldrich at Aachen University and chemistry professors Eva Zurek and Larkin Professor of Chemistry Jochen Autschbach at the University of Buffalo. Curium is element 96 in the periodic table. It is one of the highest numbered elements that exists in sufficient quantities to be visible to the naked eye.
The team has been researching how curium reacts to extremely high pressure when squeezed between two diamonds. It turns out that the outer electrons of curium change their behavior in a way that alters the ability of the element to bond with other elements when the distance to surrounding lighter atoms is reduced. Albrecht-Schmitt said, “This was not anticipated because the chemistry of curium makes it resistant to these types of changes. In short, it is quite inert.”
Curium’s properties are usually totally resistant to modification, but specific curium compounds display the changes found by Albrecht-Schmitt and his team. The contribution of Albrecht-Schmitt is related to the wider mission of his laboratory to enhance our understanding of heavier elements also known as actinides.
In 2016, the Department of Energy (DoE) gave Albrecht-Schmitt a grant of ten million dollars to establish the Center for Actinide Science and Technology (CAST). The purpose of the Center is to concentrate on accelerating scientific advancements toward better management of nuclear waste.
The heavier elements in the periodic table have been known for decades but they are still largely a mystery to scientists, especially when compared to what is known about lighter elements such as nitrogen and oxygen. Albrecht-Schmitt said, “It's an exciting experiment that showed that we have much greater control of the chemistry of these difficult to control elements than previously thought.”
Autschbach said, “The curium (3+) ion we studied has a half-filled outer electron shell that is very difficult to engage in chemical bonding. An integrated experimental and theoretical approach showed that the application of high pressure to a crystal contained curium (3+), along with sulfur-organic and ammonium ions, causes the outer shell of curium to participate in covalent chemical bonding with sulfur. This may help guide new ways of studying the mysterious behavior of chemically resistant actinide shells.”
As more is learned about the heavier side of the periodic table, scientists are discovering new strategies to control processes of chemical separation. These may lead to the design of resilient materials for long-term storage of radioactive elements and nuclear recycling. New knowledge revealed by squeezing heavy elements between diamonds could also be used to manipulate other elements.
It would not be practical to apply these extreme pressure techniques to a stream of nuclear waste in order to force chemical bonding that would reduce the radioactivity of the nuclear waste. However, what is learned about physical and chemical manipulation of very heavy elements may some day lead to the development of techniques that could be applied to reduce the danger of nuclear waste.