Vacancy segregation and intrinsic coordination defects at (111) twist grain boundaries in diamond

High radiation damage resistance has become increasingly important for applications of functional materials in harsh environments. The high radiation damage resistance diamond cubic carbon is a unique material which is considered for radiation environments. Beyond the intrinsic radiation hardness of crystal, the interaction between point defects and interfaces (e.g., grain boundaries) increases resistance to radiation damage. In effect, grain boundaries act as sinks for point defects and promote their mutual annihilation. Furthermore, interfaces can be exploited to obtain controlled segregation of point defects, thus avoiding the degradation of material properties due to uncontrolled point defect segregation and coalescence. In the present work, we investigate the interaction between vacancies - as a radiation defect in the bulk crystal - and (1 1 1) twist grain boundaries in crystalline diamond using atomistic simulation with analytical bond order potential. Based on previous observations on structure-property relationships characterising the (1 1 1) twist grain boundaries, this work analyses the emergence of periodic segregation patterns, which are rationalised by the underlying interface structure and their periodic intrinsic coordination defect populations. This observation suggests that randomly distributed vacancies in bulk single crystals can form self-organised defect arrays in the grain boundary. The coordination defect content correlates with the interface sink efficiency, providing guidelines for designing interfaces with high sink efficiency.