The molecular dynamics simulation method has been used to study the size- and shape-dependent lattice parameter of unsupported small Pt nanoparticles, where the shapes concerned are sphere, cube, and cuboctahedron. It is shown that the lattice parameters decrease with decreasing the particle size in specific shape. The lattice variations of cubic shapes are higher than those of cuboctahedral shapes, and those of cuboctahedral shapes are higher than spherical ones. Furthermore, the shape effect on lattice parameter increases with decreasing the particle size. By linear fitting the simulated results, it is found that the particle shape can contribute to 7% of the total lattice parameter variation for cubic shape and to 5% for cuboctahedral shape. The present simulation results are qualitatively consistent with experimental values and the predictions by Continuous-Medium (CM) model.
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This work was supported by Postdoctoral Science Foundation of Central South University, China Postdoctoral Science Foundation (no. 20070420185), and National Natural Science Foundation of China (no. 50401010).
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