Diamonds and new forms of ‘superhard’ carbon

‘Superhard’ materials are capable of slicing, drilling and polishing other objects. Additionally, they hold potential for creating scratch-resistant coatings which could help keep expensive equipment safe from potential damage. Using computational predictions of crystal structures combined with machine learning, scientists have undergone theoretical research on these materials – they have predicted new carbon structures but are yet to create them.

Researchers who recently conducted the study identified 43 previously unknown forms of carbon. These are thought to be both stable and ‘superhard’, with several of them predicted to be slightly harder than or nearly as hard as diamonds. Hardness relates to a material’s ‘ability to resist deformation’. A substance is considered ‘superhard’ if it has a hardness value of more than 40 gigapascals – this is measured through an experiment known as the Vickers hardness test. All 43 of the newly identified carbon structures are estimated to adequately meet this threshold. Further, three are predicted to exceed the Vickers hardness of diamonds. Some of the hardest structures found even contained fragments of diamond and lonsdaleite (also known as ‘hexagonal diamond’) in their crystal lattices.

Further, the study also suggests that a number of carbon structures which have previously been described by other teams of researchers will also be ‘superhard’. The techniques used in this study may be applied to identify such other ‘superhard’ materials, including ones which contain elements other than carbon. For example, co-author of the study, Dr Eva Zurek, suggests that ‘one thing that we know about superhard materials is that they need to have strong bonds […]. Other elements that are typically in superhard materials come from the same side of the periodic table, such as boron and nitrogen’.

Students applying for Natural Sciences, including those with an interest in topics concerning physical sciences, can consider how theoretical research such as this can lead to potentially innovative and novel material developments in the near future.