Abstract
Using first-principles density functional theory calculations, we find dramatically different electronic
states in the C chains generated on the H-terminated C(111) surface, depending on their length and parity.
The infinitely long chain has p electrons completely delocalized over the chain, yielding an equal
C-C bond length. As the chain length becomes finite, such delocalized p electrons are transformed into
localized ones. As a result, even-numbered chains exhibit a strong charge-lattice coupling, leading to a
bond-alternated structure, while odd-numbered chains show a ferrimagnetic spin ordering with a solitonlike
structure. These geometric and electronic features of infinitely and finitely long chains are analogous
to those of the closed (benzene) and open (polyacetylene) chains of hydrocarbons, respectively.