Ultra-high thermal conductivities of tetrahedral carbon allotropes with non-simple structures

Pursuing high thermal conductivity is of great significance to enhance the performance and working stability of microelectronics in terms of efficient heat dissipation. Traditionally, ultra-high thermal conductivity is thought to exist only in simple crystals with few atoms in the primitive cell, such as diamond and boron arsenide, where the phonon-phonon scattering is weak. In this study, we report an innovation from conventional knowledge based on state-of-the-art first-principles calculations. It is found that the thermal conductivities of three carbon allotropes of C₃₂, C₃₆, and C₉₄ with non-simple structures can be as high as 1152.75, 1075.70, and 860.07 W m^-1 K^-1, respectively, despite a large number of atoms in the primitive cell. Through comparative analysis, it is revealed that there exist certain competitive mechanisms, where the weak phonon anharmonicity is found to dominate the high thermal conductivity. Our study not only uncovers excellent carbon-based candidates with ultra-high thermal conductivity for enhancing heat dissipation with potential applications in electronics, but also provides insights into the thermal transport, which will shed light on future studies.