Solids (Morrison) Flashcards
what is the layer stacking pattern for hexagonal cp?
ABA
what is the layer stacking pattern for cubic cp?
ABC
How many tetrahedral sites in hcp?
2 x T+ 2 x T-
in ccp what do T+ and T- share?
faces
how many T // O sites per unit cell of ccp?
8 // 4
in hcp what do T+ and T+ share?
corners
in hcp what do T+ and T- share?
edges
in hcp what do O and T sites share?
faces
Rocksalt describe:
ccp (either Na or Cl)
all O sites filled; T sites empty
edge sharing NaCl6 and ClNa6 octahedra
Zinc Blende describe:
ccp S2- with Zn2+ in 1/2 T sites
all O and 1/2 T empty
corner sharing ZnS4 and SZn4 tetrahedra
Wurtzite describe:
hcp S2- with Zn2+ in 1/2 T sites
all O and 1/2 T empty
corner sharing ZnS4 and SZn4 tetrahedra
Nickel Arsenide describe:
hcp As with Ni in all O sites
all T sites empty
Face sharing NiAs6 octahedra, edge sharing AsNi6 trigonal bi-prisms
Fluorite describe:
ccp Ca2+ with F- in all T sites
all O sites empty
edge sharing CaF8 cubes, edge sharing FCa4 tetrahedra
Rutile describe:
hcp O with Ti in 1/2 O sites [distorted]
1/2 and all T sites empty
layers of edge sharing TiO6 octahedra and edge sharing OTi3 trigonal planar
ReO3 describe:
based on primitive cubic
cubic Re lattice with O2- on the midpoints
corner sharing RO6 octahedra
Perovskite describe:
ABO3 - based on primitive cubic
cubic B lattice with O on the midpoints and A central
face sharing AO12 cuboctahedra, corner sharing BO6 octahedra, face sharing OA4B2 distorted octahedra
Spinel describe:
ccp
AB2X4 array with A in 1/8 T sites, B2 in 1/2 O sites
T-T isolated, T-O corner, O-O edge
unconnected tetrahedra and edge sharing octahedral
Inverse spinel describe:
ccp
AB2X4 array with B in 1/8 T sites, A+B in 1/2 O sites
edge sharing BO6 + AO6 octahedra, BO4 tetrahedra unconnected, corner shared with octahedra.
how do you find the radius ratio?
r+/r-
What are some rules to determine radius ratios? (6 things)
based purely on ionic model
hard spheres // only electrostatic forces // maximise CN // avoid C+C+ and A-A- interactions // maintain local electroneutrality
What are some general size relationships for atomic radii? (7 things)
radii increase down a period // isoelectric series - size decreases with increased charge // radius decreases with increased oxidation state // radius increases with increasing CN // for a given OxS radius decreases –> // for a given 3D element, r(HS) > r(LS) // diagonal relationships: r(Na+)~r(Ca2+)
what is the minimum cation size for an octahedral site?
0.414
what is the minimum cation size for an 8-coordination site?
0.732
what is the minimum cation size for a tetrahedral site?
0.225