Dual structural transition L12 → FCC and further FCC → Ih is shown to be possible under the thermal factor in Cu3Au and Cu-Au clusters with the diameter up to 3.0 nm.

So, thermal stability limits were studied for the initial L12 phase in Cu3Au nanoalloy clusters up to 8.0 nm and Cu-Au clusters up to 3.0 nm at various degrees of Au atom concentration, with molecular dynamics method using a modified tight-binding TB-SMA potential.

Therefore, to theoretically determine catalytic properties, one needs to use a most real structural model complying with Cu-Au nanoparticles under various external influences. However, providing the reaction capacity of alloy nanoparticles the surface electronic structure strongly depends on their atomic ordering. This study demonstrates that the interplay between packing, structural transition and shape can be utilized to develop new nanomaterials with controlled properties.Ĭu-Au alloy nanoparticles are known to be widely used in the catalysis of various chemical reactions as it was experimentally defined that in many cases the partial substitution of copper with gold increases catalytic activity. The current results highlight possible mechanisms for controlling the physical properties of matter at the nanoscale through their morphological characteristics. The disturbing the spherical shape of small FCC nanoparticles is found to be easier than breaking them across planes. Our predictions show that bulk-to-nano transition starts at, in a good agreement with the relevant literature. Compared to the bulk phase, the volume packing fraction (f) of a FCC nanoparticle decreases with size and approaches 0.810 at shells greater than 208. These values are smaller than the maximum values of their bulk counterparts. For both structures, ’s are maxima at radii equal to the nearest neighbor distances. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 8-1.We report on the development of a simple and efficient method to predict the structural transition and the bulk-to-nano transformation of spherical FCC and BCC solid nanoparticles using the surface atomic packing fraction (). Materials: engineering, science, processing and design (1st ed.). Ashby, Michael Hugh Shercliff David Cebon (2007).Introduction to the Thermodynamics of Materials (4th ed.). Why Things Break: Understanding the World by the Way It Comes Apart. Materials Science and Engineering: An Introduction 9th Edition, Wiley 9 edition (December 4, 2013), ISBN-13: 978-1118324578. Department of Energy, Material Science. DOE Fundamentals Handbook, Volume 2 and 2. January 1993. Department of Energy, Material Science. DOE Fundamentals Handbook, Volume 1 and 2. January 1993. This structure, along with its hexagonal relative (hcp), has the most efficient packing (74%). For example, metals with a high atomic packing factor will have a higher malleability or ductility, similar to how a road is smoother when the stones are closer together, allowing metal atoms to slide past one another more easily.įor example, in a fcc arrangement, a unit cell contains (8 corner atoms × ⅛) + (6 face atoms × ½) = 4 atoms. In materials science, the atomic packing factor of a unit cell explains many properties of materials. The radius of the spheres is taken to be the maximum value such that the atoms do not overlap. January 1993.īy convention, the APF is determined by assuming that atoms are rigid spheres. DOE Fundamentals Handbook, Volume 1 and 2. In crystallography, atomic packing factor (APF), packing efficiency or packing fraction is the sum of the sphere volumes of all atoms within a unit cell (assuming the atomic hard-sphere model) divided by the unit cell volume.

Atomic packing factor for bcc and fcc