Diamond Finally Meets Its Match

For quite some time now, people have looked at diamonds as being the most tough, naturally occurring materials on Earth. But that wisdom is about to be challenged by a mathematical model, which says that a new, exotic form of carbon has the ability to break the ultra-tough inner structure of the diamond. And, beyond theory, experts consider that the material has already been obtained, as far back as 2003, but that the team working on it at the time had no idea what they had come across. According to the model, the material is a hybrid between the soft carbon-compound graphite and diamonds. Its special structure provides it with the ability to crack its transparent “relatives,” while remaining relatively unharmed.

Chinese researcher Yanming Ma, from the Jilin University, in Changchun, and his team, working together with colleagues from the United States, have predicted the new material through theoretical calculations. They also believe that the new form of carbon has already been obtained by expert Ho-kwang Mao, from the Carnegie Institution of Washington, back in 2003. During the experiments, Mao and his team placed graphite in a powerful press, and squashed it as hard as they could. They noted the formation of a new material, which was able to break off the teeth of the diamond press.

Mao, who is also a co-author of the new study, says that the physical properties of the material he produced some six years ago are very similar to those inferred by the current theoretical models. In addition, the calculations also manage to explain a few phenomena that couldn't be inferred from directly obtaining the material. Chemists explain that graphite and diamond are the two single forms of pure, crystalline carbon – the first, transparent and very tough, the second, black and soft. These differences are given by the internal structure of the carbon atoms inside the materials.

While in diamonds the atoms are arranged in 3D matrices, with each of them having four neighbors, in graphite things are a bit different. The second material is made up entirely of a 2D, one-atom-thick sheet, organized in a hexagonal structure, with the layers bounding to each other only through weak forces. This is the main reason why graphite is so soft and can be easily broken apart. But, by applying high pressure to it, graphite can turn into diamond, which is the basis for artificial diamonds, used in tools and other applications, Nature News reports.

The new material, dubbed M-carbon, was observed in 2003 to not be able to hold together when the pressure was released, but, rather than being disappointed by the finds, Ma tells now that a number of applications come to mind, in which materials only become strong when pressure is applied. In addition, by making M-carbon in narrow sheets and augmenting its properties with dopants, it could be made to last in some of its weaker forms.