Solids (20% on final)

Primitive characterisitics

• 1 atom in corners (8 corners x 1/8)

• 52.3% packing efficiency

• SN = 6

• a = 2r

BCC characteristics

• 2 atoms

  • 1 in center

  • 1 on corners (8 corners x 1/8)

• 68% packing efficiency

• SN = 8

• a = (4/√3)r

• atom in center makes layers NOT slide easily

FCC characteristics

• 4 atoms

  • 1 on corners (8 corners x 1/8)

  • 3 on faces (6 faces x 1/2)

• 74% packing efficiency

  • high packing efficiency allows layers to slide easily

• SN = 12

• a = (4/√2)r

# of tetrahedral sites in FCC and where

8

• all in the center

# of octahedral sites in FCC and where

4

• 3 on edges (12 edges x 1/4)

• 1 in the center

occtant

where cations that form the interstitial alloy

Is this stable? why or why not?

Unstable

• Cation is too small to have strong attraction w/ anions

Is this stable? why or why not?

Stable

• Cation fits perfectly

• Maximizes cation-anion bonds

Is this stable? why or why not?

Stable

• Cation is kinda big

• weak anion-cation attraction

draw ideal cation fit

Antifluorite characteristics

• radius ratio: 0.225 < r < 0.414

• Tetrahedral sites (8)

• SN = 4

• FCC array

• Cation:anion unit cell ratio = 8:4

• a = 4/√3 (r_x + r_y)

Rock salt characteristics

• radius ratio: 0.414 < r > 0.73

• Octahedral sites (4)

• SN = 6

• FCC array

• Cation:anion unit cell ratio = 4:4

• a = 2r_x + 2r_y

CsCl crystal characteristics

• radius ratio: r > 0.73

• Cubic sites

• SN = 8

• BCC array

• Cation:anion unit cell ratio = 1:1

• a = (2r_x + 2r_y) / √3

Zinc blende

• radius ratio: 0.225 < r < 0.414

• Tetrahedral sites (4)

  • 50% of tetrahedral filling due

    to stoichiometry

• SN = 4

• FCC array

• Cation:anion unit cell ratio = 4:4

• a = 4/√3 (r_x + r_y)

radius ratio

r_cation / r_anion

minimum size required to occupy a gap

interstitial alloy

guest metal (super small) wedges between host metal

intermetallic alloy

when metals with strong covalent bonds form a cystalline structure

substitutional alloy

random composition; guest metal replaces some of the host metal; similar radii