  Atomic-sized lead (Pb) contacts are deposited and dissolved in an
electrochemical environment, and their transport properties are measured. Due
to the electrochemical fabrication process, we obtain mechanically unstrained
contacts and conductance histograms with sharply resolved, individual peaks.
Charge transport calculations based on density functional theory (DFT) for
various ideal Pb contact geometries are in good agreement with the experimental
results. Depending on the atomic configuration, single-atom-wide contacts of
one and the same metal yield very different conductance values.
