For centuries, alchemists pursued the dream of turning copper into diamonds, unaware that such a transformation requires a nuclear reaction. But wouldn’t it be nice if the graphite tip of a pencil could be turned into diamond? After all, they are both composed entirely of carbon atoms.
The main difference between pencil lead and the sparkling gem, which are allotypes (different forms) of carbon atoms, lies in how these atoms are arranged.
Converting graphite into diamonds requires extreme temperatures and pressures to break and reform chemical bonds, making the process impractical. A more feasible transformation, according to Prof. Moshe Ben Shalom, head of the Quantum Layered Matter Group at Tel Aviv University (TAU), involves reconfiguring the atomic layers of graphite by shifting them against relatively weak van der Waals forces.
A study describing this has just been published in the prestigious journal Nature Review Physics under the title “Sliding van der Waals polytypes.” Led by Ben Shalom and doctoral students Maayan Vizner Stern and Simon Salleh Atri of the university’s Sackler School of Physics and Astronomy, the team included post-doctoral students from India and South Korea who were not deterred by the Israel-Hamas War here.
In molecular physics and chemistry, these forces involve a distance-dependent interaction between atoms or molecules, unlike ionic or covalent bonds. These are weak electrostatic forces that attract neutral molecules to one another. Particles in liquid or air vibrate and move constantly. Thus, they collide with other particles, including the media’s particles such as water molecules. The bonds between them refer to the weakest type of bonds between covalent molecules, such as in gases, liquids, and polymers, hold molecules together loosely, and determine the stiffness and strength of materials.
IN AN INTERVIEW with The Jerusalem Post, Ben Shalom said that this technique won’t really create diamonds – which are also used for industrial purposes and have many uses in manufacturing processes.
If the switching process is fast and efficient enough, the conversion of graphite and similar “van der Waals” materials could serve as tiny electronic memory units (memory chips) that are in huge demand around the world and produced mostly in China and Taiwan. The value of these newly engineered “polytype” materials could then exceed that of both diamonds and gold.
The technology may be ready in the next few years
The professor and his colleagues at TAU have established a company on campus with the aim of eventually producing the heart of memory chips much more easily than today. “We hope to be ready in about four years. It will be a revolution,” he enthused. “Layers are the most important thing for sliding. We imported a tiny, two-centimeter cube of graphite from a mine in northern England near Manchester. It has a lot of layers, and we can work on the cube for a whole decade!”
Reacting with the external electric field, boundary strips between different structural domains may slide with superlubrication to expand the area of the more stable polytype.
“Like graphite, nature produces many other materials with weakly bonded layers,” doctoral student Stern explained. “Each layer behaves like a Lego brick. Breaking a single brick is difficult, but separating and reconnecting two bricks is quite simple. Similarly, in layered materials, the layers prefer specific stacking positions where atoms align perfectly with those in the layer next to it. Sliding between these positions happens in tiny, discrete jumps – just an atomic distance at a time.”
COMPARED WITH electronic phase transitions, structural phase transitions of crystals are challenging to control owing to the energy cost of breaking dense solid bonds.
“We are developing new methods to slide the layers into different arrangements and study the resulting materials. By applying an electric field or mechanical pressure, we can shift the layers into various stable configurations,” Atri said. “Since these layers remain in their final position even after the external force is removed, they can store information – functioning as a tiny memory unit.”
The team has also been exploring how different numbers of layers influence the properties of materials. For example, three layers of a material with two types of atoms can create six distinct stable materials, each with unique internal polarizations. With five layers, this number increases to 45 different possible structures. By switching between these configurations, researchers can control optical, electrical, and magnetic parameters, and rearrange them into six different crystalline forms, each with distinct electrical conductivities, infrared responses, magnetizations, and superconducting properties.
The main challenge is to maintain the material’s stability with structural transitions that can be controlled. Their new study summarizes ongoing studies and proposes new methods to refine this “slidetronics” switching mechanism, preparing the way for innovative applications in electronics, computing, and more.
With continued research, these sliding materials could revolutionize technology, offering faster, more efficient memory storage and unprecedented control over material properties. The ability to manipulate atomic layers with precision is opening doors to a new era in materials science – one where the most valuable discoveries may not come from creating gold, but from unlocking the hidden potential of everyday elements.