Abstract
Exceptionally long and uniform YSi2 nanowires are formed via self-assembly of yttrium atoms on
Si(001). The in-plane width of the thinnest wires is known to be quantized in odd multiples of the silicon
lattice constant. Here, we identify a new class of YSi2 nanowires that violate the odd-multiple rule. The
structure of the thinnest wire in this category is determined by comparing the normalized differential con-
ductance spectra from scanning tunneling spectroscopy (STS) with the projected surface density of states
(DOS) of various candidate models, obtained from first-principles, by means of a R-factor analysis. The
Pendry R-factor appears to be a useful indicator for selecting the best structure model from the tunneling
spectra of individual nano objects.
