Superior toughness and hardness in graphite-diamond hybrid induced by coherent interfaces

Finding a material with both a high hardness and toughness is a key area of research in materials science and condensed matter physics. Herein, we propose a new kind of superior mechanical material, a graphite-diamond hybrid (termed Gradia, Nature, 2022, 607, 486), consisting of diamond and graphite nanodomains interlocked via coherent interfaces using first-principles calculations. Upon strain, unusual sequential structural transitions appear in the Gradia, driven by the movement of coherent graphite-diamond interfaces towards the diamond units. This feature allows Gradia to withstand large strains and absorb more energy before structural collapse, leading to superior toughness. More interestingly, Gradia has the potential to be a superhard material based on the estimated Vickers hardness above 40 GPa. This work could play an exemplary role in the exploration of excellent mechanical materials through the modulation of the linking styles of carbon building blocks.

Automated summary

Finding a material with high hardness and toughness is a crucial research topic. This study introduces a new superior mechanical material called Gradia, composed of diamond and graphite nanodomains interlocked via coherent interfaces. Gradia exhibits sequential structural transitions under strain, leading to outstanding toughness. Furthermore, it has the potential to be a superhard material with estimated Vickers hardness exceeding 40 GPa. This work could be exemplary in exploring excellent mechanical materials through the modulation of carbon building block linking styles.