Advanced mechanosynthetic operations can transfer single atoms
The diagrams above illustrate several mechanosynthetic reactions on a reconstructed diamond (100) surface in vacuum (with sequential steps, left to right). Depositing and removing hydrogen protects and activates surface sites; depositing carbon extends the structure. Much as a small number of distinct computer instructions can be combined in different patterns to perform a vast range of different computations, so a small number of operations like those shown above can be combined in different patterns to build a vast range of different structures. (Other mechanosynthetic operations have been studied by computational and experimental means.)
Deposit H: A mechanical device applies a GeH tip to a C atom on the surface, forming a strong CH bond while breaking both the weak GeH bond and a weak CC pi bond on the surface. (Basis: semi-empirical quantum chemistry calculations, with bounds on differential bond energies from other sources.)
Remove H: A mechanical device applies an alkynyl radical tip to an H atom on the surface, forming a very strong CH bond while breaking a CH bond of ordinary strength. (Basis: computational studies using ab initio quantum-chemistry techniques with electron correlation.)
Deposit C: A mechanical device moves a vinylidenecarbene tip along a barrier-free path to insert into the strained alkene, twists 90° to break a CC pi bond, and then pulls to cleave the remaining CC sigma bond. (Basis computational studies using density functional theory.)
How can mechanical devices move and apply molecular tools?
How can nanoscale operations be used in building large objects?
References (with full text):
Musgrave, C.B., Perry, J.K., Merkle, R.C., Goddard III, W.A. “Theoretical studies of a hydrogen abstraction tool for nanotechnology” Nanotechnology 2:187-195 (1991).
Walch, S.P., Merkle, R.C. “Theoretical studies of diamond mechanosynthesis reactions” Nanotechnology 9:285-296 (1998).