Cataloged from PDF version of article.The fabrication of stable gold monoatomic chains suspended between two gold
electrodes is one of the milestones in nanoscience and technology, since miniaturization
of the electronic components is one of the great importance in development
and improvement of new devices in nanoelectronic. Monoatomic chain nanowires
show unusual mechanical and electronic properties such as quantized conductance
and much stiff bonds compare to the ones in bulk. Ohnishi et al. [1], has visualized
the monoatomic chains by using transmission electron microscopy (TEM).
At the same time, Yanson et al [2], have produced the monoatomic chains and
they measured its conductance. In the bond length measurement of monoatomic
chains, unusually long interatomic lengths have been observed compare to interatomic
distances in the bulk and dimer. In order to understand the nature of
bonding and unusual structural properties, in this thesis, mechanical and electronic
properties of metal chain nanowires are investigated from first principles
by using pseudopotential plane wave calculations. Six different metals (Au, Ag,
Al, Cu, Pt and Na) are studied in detail. All metals under study show two wire
structure which are linear and zigzag structure. Au, Al and Pt show two different
zigzag structure. All the wires are metallic. Relative stabilities are investigated
by calculating the tension corresponding to apply force to keep the wire at a
specific length. Au and Pt have bigger breaking force at breaking point relative
to other metallic wires. In this thesis, effect of H, H2 and C impurities on mechanical
and electronic properties of Au monoatomic chains are also studied. In
wires with H and C impurities, wire under tension break from Au-Au bond away
from the impurity. However, wire break from Au-H bond in H2 system. Except
from Au-H system, wire become insulator when it contain C or H2 impurities.
Before breaking, Au-impurity-Au bond length is in the range of long interatomic
distance observed in experiment. So, the presence of an impurity can explain
the observed long interatomic distances. However, changing of bond lengths and breaking bond during the stretching of wire depends on the type of impurity.
If one stretch the Au-H system, all bond lengths increase in the same amount
before breaking. However in Au-C system, Au-Au bond length away from the C
impurity increase much more than other bonds. It is shown that absorption of
impurity atoms modify the stiffness of the bonds in the wire. This related to the
charge transfer from Au to impurity (for H and C). In H and C systems, wire
break from Au-Au bond away from the impurity. However in H2 system, wire
break from Au-H bond.Çakır, DenizM.S