  Bimetallic nanoalloys such as nanoparticles and nanowires are attracting
significant attention due to their vast potential applications such as in
catalysis and nanoelectronics. Notably, Pd-Pt nanoparticles/nanowires are being
widely recognized as catalysts and hydrogen sensors. Compared to unary systems,
alloys present more structural complexity with various compositional
configurations. Therefore, it is important to understand energetically
preferred atomic structures of bimetallic nanoalloys. In this study, we
performed a series of simulated annealing Monte Carlo simulations to predict
the energetically stable atomic arrangement of Pd-Pt nanoparticles and
nanowires as a function of composition based on a set of carefully designed
empirical potential models. Both the Pd-Pt nanoparticles and nanowires exhibit
quasi-ordered configurations, quite similar to bulk alloy phases such as the
$\rm L1_0$ and the $\rm L1_2$ structures with substantial surface segregation
effects. We believe that this study can provide a theoretical guide for the
design of various bimetallic nanomaterials.
