  Recently (PRL 96, 106804 (2006)) it was suggested that cobaltocene(CC)
molecules encapsulated into (7,7) carbon nanotubes (CNT@(7,7)) could be the
basis for new spintronic devices. We show here based on impact molecular
dynamics and DFT calculations that when dynamical aspects are explicitly
considered the CC encapsulation into CNT@(7,7) does not occur, it is prevented
by a dynamic barrier mainly due to van der Waals interactions. Our results show
that CNT@(13,0) having enough axial space for encapsulation but no enough one
to allow freely rotation of the cobaltocene molecule would be a feasible
candidate to such application.
