Nucleation and anomalous cap formation on icosahedral Fe13 nanocatalyst: A first step towards chirality-controlled single-walled nanotube growth

Symmetric minima of surface potential energy of an icosahedral Fe13 nanocatalyst act as nucleation sites for chirally selective initial growth of single walled carbon tubes at low temperatures. The nucleation sites are sites of maximum coordination number of the adsorbed carbon. We show this using the fivefold symmetry of a pentagonal pyramid of an icosahedron. Initial zigzag structure from nucleation sites results in formation of hexagons and pentagons that result in anomalous cap formation. Possible cap lift off mechanism is discussed.