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When carbon and nitrogen meet under pressure

2026/03/092026/03/19

Three recent papers expand understanding of chemistry relevant to biology and industry

When it comes to the chemical elements, few are simultaneously as ubiquitous and necessary as carbon and nitrogen. They form the backbone of life, they enable many catalytic processes used in industry, they lie at the heart of many key materials in our everyday lives, and they make up over 78% of the composition of our atmosphere (almost all of that amount being nitrogen). Their chemistry has been widely studied for centuries, forming the foundation of organic chemistry and revealing entire libraries’ worth of reactions across inorganic chemistry. That chemistry forms the basis for common methods in mining, electroplating, pharmacology, and much more. But an international research team led by scientists at the Goethe University Frankfurt have shown that this familiar picture only accounts for a small fraction of what carbon and nitrogen can do—one just has to turn up the heat and the pressure. A series of studies published in the Journal of the American Chemical Society (JACS) and Angewandte Chemie International Edition reveal that under high pressure, carbon and nitrogen can simultaneously react with a variety of metals. The results could have a strong influence on future functional materials.

Carbon and nitrogen from very stable compounds. Molecular nitrogen N₂ in the atmosphere, in particular, forms triple bonds that require a large amount of energy to break, and solid elemental carbon can be arranged to make diamonds, among the hardest and most corrosion-resistant compounds known. While carbon and nitrogen do react at ambient pressure forming cyanogen (CN)₂ – a colorless toxic gas — their behavior can completely change under high pressure.

However, the studies ley by scientists from the Goethe University Frankfurt revealed new pathways to make novel carbon-nitrogen anions through the use of extreme pressures. By pressing the reacting substances between two diamonds—in a device called a diamond anvil cell—while simultaneously heating the reactants at high precision using lasers, the team could get the nitrogen and carbon to bond together forming negatively charged ions, which are stabilized in novel compounds with positively-charged metallic ions.

Image: Using diamond anvil cells and laser heating, the research team has been able to produce new kinds of chemical reactions with ultra-stable carbon and nitrogen atoms, allowing them to form novel compounds with metals such as bismuth, cadmium, calcium, and europium.

Credit: Goethe University Frankfurt

Read more on DESY website

Microscopic origins of electrical conductivity in superheated solids revealed

2021/04/022021/04/15

Scientists used terahertz radiation for measurements of strongly excited material

In-depth understanding of the electrical conductivity of matter is the key to many cutting-edge research and applications, ranging from phase-change memory in microelectronics to magnetospheres rooted in planetary interiors due to the motion of the conductive fluid. Unique states of material created by ultrafast table-top lasers or free-electron lasers (FEL) allow us to gain insight into atomic levels. However, it also requires sub-picosecond resolution to capture the details on the timescale of atomic motion. Therefore, in conductivity measurements it prevents the use of contact diagnostics such as multimeter and four-point-probe. Although ultrafast optical or X-ray measurements can provide information on high frequency electrical conductivity, they require complex models to extrapolate the intrinsic direct current (DC) conductivity of material.

The terahertz radiation (1 THz= 10¹²Hz (cycles per second)) offers a unique solution to tackle this dilemma. The THz electromagnetic wave behaves like DC electric-field to the sample because the oscillation of its electric field is slow compared to the electron momentum relaxation frequencies in solid and liquid materials (typically 10¹³Hz or larger), and the width of each THz cycle is short enough to resolve sub-picosecond dynamics. Nevertheless, to measure the conductivity of strongly excited materials in the irreversible regime still requires high brightness THz radiation in order to penetrate the dense electron cloud as well as high sensitivity to detect the THz temporal profile in a single shot.

An international research team, led by scientists from the SLAC National Accelerator Laboratory and DESY, have recently measured the electrical conductivity of strongly heated material using the THz FEL radiation at FLASH. In this study, gold nano-foil samples were heated by the FLASH extreme ultraviolet (XUV) FEL pulses to electron temperatures up to 16,000 °C. As the thermal energy transfers from the electrons to the ions, the sample transits from cold to superheated solid and eventually melts into warm dense liquid. The researchers have determined the DC electrical conductivity by measuring the transmitted THz electric field through the heated samples. The multi-cycle THz pulses from FLASH provide continuous measurements with temporal resolutions better than 500 femtoseconds.