A team of researchers from Bar Ilan discovered the reason for the diamond's strength

The carbon atoms that are not directly connected to each other repel the other atoms and this force prevents the diamond from shrinking, explains Prof. Shmarihu Hoz, who headed the research group in a conversation with the Hidan site. The article is published in a journal dedicated to research in physical chemistry and according to Hoz it will provide tools for the development of even stronger materials * The team also includes Prof. Eli Altus from the Technion

A team of scientists from Bar-Ilan University managed to crack the secret that makes the diamond so hard. We all know that diamond is the strongest material in nature and for years many scientists around the world have studied the reason for this. Now the solution is found precisely in Israel.

The team of researchers, led by Prof. Shmariahu Hoz from the Chemistry Department at Bar Ilan University, discovered that the interactions between the atoms in the diamond, which are not directly related to each other, are the main cause of the difficulty. "As we know, a diamond is composed of pure carbon," explains Prof. Huz. "Each carbon atom in a diamond is surrounded by four additional carbon atoms directly bonded to it, and each of these atoms is bonded to three additional carbon atoms. This is how a special structure is created in the composition of the diamond in which, around each atom there are 12 carbon atoms that are not related to it. In the research we discovered that the repulsion between these atoms is one of the main reasons why the diamond is so hard."

This discovery, which will be published in the next issue of the scientific journal The Journal of Physical Chemistry, could lead to the development of additional materials that will excel at a particularly high degree of difficulty, and perhaps even higher than that of diamond.

This is not the first time that this team of scientists has discovered important phenomena in the study of materials. The research group, which as mentioned includes Prof. Shmariahu Hoz, Prof. Harold Bash and Dr. Lior Itzhaki from the Bar-Ilan Chemistry Department, and Prof. Eli Altus from the Technion, has been engaged for several years in researching the validity of the laws of mechanical engineering in the nanometer world, and recently even revealed the existence of synthetic molecular rods whose strength is 40 times greater than that of a diamond. "The study of the nano world (whose units are measured in thousands of microns) using the tools of mechanical engineering, may be of great importance in expanding human knowledge as well as in the applied field." Prof. Hoz says.

In a conversation with the science website, Prof. Hoz explains: "Mechanical engineers use different tools to test materials. Using these tools it is possible to check the hardness of materials, their flexibility, when they break, etc. We tried to use these tools at the nanomolecular level and first started to examine whether rods, whose strongest structure as used in railway tracks and building beams, are also the strongest structure at the nanometric or molecular level. It turns out that this is not the case.

The strongest beam that engineers use is the so-called I BEAM, whose cross-section resembles the letter I, as seen in railroad tracks and beams that make up the skeleton of buildings. One of the questions we ask in our research is to what extent such a truth is also true in the nano world. "

"During the search we investigated different rods based on different materials and therefore also have different shapes. One of the rods we tested presented a strange phenomenon - when we stretched and compressed it, the "wrong" parts that we hadn't thought about bore the brunt of the contraction or stretching. When we looked carefully at these parts, we saw that what prevents the second unit from collapsing, shrinking or stretching (depending on the action we performed) these are the NON BONDED INTERACTION - interactions between atoms that are not directly related to each other."

What is meant by bonds between atoms that are not directly bonded?

Prof. Hoz: "When you look at a diamond, you see that it is made up of carbon atoms joined together. Carbon has four bonds and is therefore surrounded by four other carbon atoms to which it is bonded. Choose any one carbon atom and call it the central atom of the diamond. Of course, four other carbon atoms surround it in space. Each of them is connected to the central atom and three others, that is, in the vicinity of the central atom there are 12 more atoms (the 4 nearest neighbors to which it is connected and another 3 to which each of these neighbors is connected). These atoms are at a relatively small distance from the central atom and there is a repulsion between them and the central atom. When you press on an atom in a diamond, you decrease these distances and the repulsion increases. This is probably, we assume, the reason why diamond is so hard. There is another reason for the difficulty of the diamond and it is the classical reason. As we know, most matter (except for metals or noble gases) consists of separate molecules of matter. There are large gaps between the separates. When you press on the substance, what is compressed is not the molecules themselves, but the spaces between them are reduced. A diamond, compared to a normal substance, if it is perfect, is one big molecule and therefore difficult to compress, but there are still metals that are also one big molecule but they are not that strong. The reason for the excess hardness according to our proposal is those interactions between atoms that are not directly related to each other."

What makes these atoms repel each other and the "central" atom?

"By and large, this is the familiar repulsion between electron clouds: Inter-electronic Repulsion. Between any two molecules such as nitrogen molecules for example, the electrons repel each other and as a result the molecules bounce back to move away. As you try to bring them closer, the energy required for this increases. When the atoms are bonded together, the energetic gain of the bond offsets this repulsion and even more so, but when they are not bonded as in our case the 1 with the 12, it is a net repulsion effect."

How do you think the discovery will help to develop stronger products?

"Broadly speaking, when looking for something there are two options, one - trial and error, you try all the materials in the world, test material material, maybe you will find something, like looking for cures for cancer, and the second option is to try to understand the phenomenon and, based on the understanding, build a strategy to synthesize such materials. The understanding we have found here, assuming it is correct, may be one of the candles that will light the way to an intelligent synthesis of materials that will be harder than a diamond.

After publication, other scientists will try to verify the discovery, are you ready for that?

We came up with the idea, which is a kind of projection of a phenomenon known elsewhere in nature also on the diamond, and now it is the turn of the scientific community to investigate and verify or try to disprove the discovery. We move on anyway. Our innovation is in this modest donation. According to the professional literature in the field, this is the first time someone has come to such an insight and we hope it is true.