Towards mechanosynthesis of diamondoid structures: I. Quantum-chemical molecular dynamics simulations of sila-adamantane synthesis on hydrogenated Si(111) surface with the STM

The controlled manipulation of silicon atoms and silylene molecules at the subnanometer scale via the scanning tunnelling microscope (STM) tip provides a potentially powerful way of building silicon diamondoid structures. In this paper, we use quantum-chemical atomistic simulations to explore the feasibility of sila-adamantane mechanosynthesis on a hydrogenated Si(111) surface using the STM tip. A sequence of energetically favourable insertion reactions is established leading to stable surface intermediates and finally to the simplest silicon diamondoid structure. The sequence is based solely on these three reactants with the overall charge neutrality of the structure maintained. We characterize reaction rates and energy flows, and conclude that they are sufficiently fast and simple to make this mechanosynthesis feasible.