Molecule fragment
Moieties are the smallest building blocks handeded in the advanced mechanosynthesis of technology level III and II. When a simple resource molecule is picked up with an empty tooltip one always ends up with a few atoms on the tooltip. Some bonds need to be broken open to make it a reactive radical ready for deposition. It is generally not necessary to prepare the picked up molecule down until only one atom is left. That is in most cases one does not put down single atoms but small moieties (always bond molecules). Most often unused bonds are left hydrogen capped and and only one or two bonds are actively used - the one to the tooltip and the one to the workpiece. Hydrogen and oxygen with one and two bonds respectively are subject for single atomic deposition. The heavier elements of the same groups - the halogenes calcogenes - too.
simple respurce molecules
For mechanosynthesis of diamond ethyne C2H2 methane CH4 and traces of digermane Ge2H6 can be used. This has been toroughly analyzed.
Further molecules of prime interest are carbon dioxide CO2 water H2O and nitrogen gas N2. The capability of handling those allows for tappingn the air as a resource for products that (almost) exclusively contain diamondoid molecular elements out of hydrogen carbon oxygen and nitrogen (HCON).
From the metals Aluminum and Titanium would be