Direct observation and catalytic role of mediator atom in 2D materials

Dr Alex W Robertson and collaborators from institutions in Korea, the USA and France, have looked beyond the Stone-Thrower-Wales concept of atom bond rotation.  They demonstrate in their paper, published in Science Advances, that undercoordinated atoms induce bond formation and breaking, with lower energy barriers (which they refer to as 'mediator' atoms).

The paper reports on the direct observation of mediator atoms in graphene defect structures using aberration-corrected transmission electron microscopy and annual dark-field scanning transmission electron microscopy, explaining their catalytic role by tight-binding molecular dynamics simulations and image simulations based on density functional theory calculations.

This study of mediator atoms will pave a new way for understanding not only defect transformation but also the growth mechanisms in two-dimensional materials.