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PY4007 Lecture 3 - Catalysts

PY4007 Lecture 3 - Catalysts. At the nanoscale, physics and chemistry converge. Catalytical effect vs cluster size. Face-centred cubic metal. [001]. [010]. [100]. Direction vectors take square brackets. FCC planes. This is a (100) plane in a FCC packed material. FCC planes.

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PY4007 Lecture 3 - Catalysts

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  1. PY4007 Lecture 3 - Catalysts At the nanoscale, physics and chemistry converge

  2. Catalytical effect vs cluster size

  3. Face-centred cubic metal [001] [010] [100] Direction vectors take square brackets

  4. FCC planes This is a (100) plane in a FCC packed material

  5. FCC planes This is a (110) plane in a FCC packed material

  6. FCC planes This is a (111) plane in a FCC packed material

  7. Surface energies of low-order planes Looser packing. Closest packing. Lowest surface energy. Higher surface energy.

  8. Wulff construction Equilibrium shape is the inner envelope of planes normal to, and passing through the end of, the free energy vectors.

  9. Equilibrium Wulff shape Create (111) faces to give truncated octahedron. (100) type face (111) type face

  10. Variations of facet sizes

  11. Multiply twinned particles

  12. Decahedral and icosahedral MTPs Made from 5 tetrahedral units Made from 20 tetrahedral units

  13. Strain in MTPs 7.5°

  14. Cluster structure of Al13

  15. Evaporation cluster source

  16. Abundances of Na clusters

  17. Closed electronic shells for Na clusters Here we are plotting:

  18. Metal-nonmetal transition in electronic states

  19. Worked example (a) Show that the Fermi energy for sodium is approximately 3.1 eV (density of Na is 970 kg m-3; atomic mass for Na is 23). [Hint: Assume a free-electron model for the valence electrons of sodium.] (b) Hence derive an approximate expression for the temperature of the metal-nonmetal transition for a sodium cluster of diameter, d. Find this diameter at a temperature of 100 K.

  20. Coulomb blockade

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