today we test the clickers again. we now venture into the world of metals metals
TRANSCRIPT
Metallic xl Structures
1) Face-Centered Cubic (FCC)
2) Body-Centered Cubic (BCC)
3) Hexagonal Close-Packed (HCP)
FCCAtoms at 8 corners & 6 faces
Equivalent of ? whole atoms.
Atomic Packing Factor (APF)= .74
Fig. 3.1
A scanning tunneling microscope (STM) is an instrument for imaging surfaces at the atomic level.
What’s an STM image?
• 1990: IBM scientist Don Eigler used an STM to move single xenon atoms on a nickel surface
•The engineers moved 35 atoms to spell out "IBM" in a 10 micrometer logo.
A scanning electron microscope (SEM) produces images by scanning a sample with a focused beam of electrons. Yields topography and composition.
What’s an SEM image?
HCP
Atoms at 12 corners, 3 in interior, 2 centered on basal planes
Equivalent of ? whole atoms
(APF)= .74Fig. 3.3
SEM of Fine Cadmium powder
http://www.sciencephoto.com/media/8998/enlarge
SEM of ZnO nanowireshttp://www.lac.tu-clausthal.de/en/arbeitsgruppen/angewandte-photonik-
lac/projekte/zinc-oxide-nanowires-for-photonic-applications/
Hexagonal structure
Metallic xl Structures
Body-Centered Cubic (BCC) APF = 0.68
Na, Fe, Cr, Mo, W
Face-Centered Cubic (FCC) APF = 0.74
Cu, Al, Ag, Au, Pb, Ni, Pt
Hexagonal Close-Packed (HCP) APF = 0.74
Ti, Zn, Cd, Co, Mg
A systematic study of symmetric tilt-boundaries in hard-sphere f.c.c. crystals
Abstract
A new method is developed for the search of mechanically stable
configurations of symmetric tilt boundaries in hard sphere f.c.c.
crystals. The problem of finding out relative displacements which
minimize the total volume of two crystal blocks forming a boundary, is
simplified to a problem of positioning a single atom sphere relative to a
block which consists of real and “image” atoms; the latter are placed in
such a way to reflect the arrangement in the other crystal block. The
method (the image atom method) has been applied to the analysis of
symmetric coincidence boundaries with [100], [110] and [111] tilt axes
with ∑-values 3–103. For the [100] (013)∑5 boundary, the procedure of
the analysis is described in detail; the derived structures are compared
with those by computer simulation. Numerical data are given in
tabulated forms for some boundaries.
Family of Directions: <1 1 0>
y
x
z
Unit cube
1= [1 1 0]
2 = 3= [1 1 0]
4 = [1 1 0]
5 = [1 1 0]
4 3
12
5
Wednesday:
Clicker Questions will include finding
Crystallographic Planes and Crystallographic
Directions
Solved Examples posted on Canvas