  In this paper we investigated structural, electronic and magnetic properties
of 3d (light) transition metal (TM) atomic chains using first-principles
pseudopotential plane wave calculations. Periodic linear, dimerized linear and
planar zigzag chain structures and their short segments consisting of finite
number of atoms have been considered. Like Cu, the periodic, linear chains of
Mn, Co and Ni correspond to a local shallow minimum. However, for most of the
infinite periodic chains, neither linear nor dimerized linear structures are
favored; to lower their energy the chains undergo a structural transformation
to form planar zigzag and dimerized zigzag geometry. Dimerization in both
infinite and finite chains are much stronger than the usual Peierls distortion
and appear to depend on the number of 3d-electrons. As a result of
dimerization, a significant energy lowering occurs which, in turn, influences
the stability and physical properties. Metallic linear chain of Vanadium
becomes half-metallic upon dimerization. Infinite linear chain of Scandium also
becomes half-metallic upon transformation to zigzag structure. An interplay
between the magnetic ground state and atomic as well as electronic structure of
the chain has been revealed. The end effects influence the geometry, energetics
and magnetic ground state of the finite chains. Structure optimization
performed using noncollinear approximation indicates significant differences
from the collinear approximation. Variation of the cohesive energy of infinite
and finite-size chains with respect to the number of 3d-electrons are found to
mimic the bulk behavior pointed out by Friedel. The spin-orbit coupling of
finite chains are found to be negligibly small.
