Importance of Interfacial Structures in the Catalytic Effect of Transition Metals on Diamond Growth.

Here, using ab initio calculations, we investigated the interaction between transition metals (M) and diamond C(111) surfaces. As a physical parameter describing the catalytic effect of a transition metal on diamond growth, we considered interfacial energy difference, ΔE int, between 1 × 1 and 2 × 1 models of M/C(111). The results showed that the transition-metal elements in the middle of the periodic table (groups 4-10) favor a 1 × 1 M/C(111) structure with diamond bulk-like interfaces, while the elements at the sides of the periodic table (groups 3, 11, and 12) favor a 2 × 1 M/C(111) structure with the 2 × 1 Pandey chain structure of C(111) underneath M. In addition, calculations of MC carbide formation for early transition metals (groups 3-6) showed that they have a tendency to form MC rather than M/C(111), which explains their low efficiency as catalysts for diamond growth. Further analysis suggests that ΔE int could serve as another parameter (catalytic descriptor) for describing catalytic diamond growth in addition to the conventional parameter of the melting temperature of M.