Problem 1: 50 points – 10 per part
The description of KAlF4 in Rohrer Table 3B.38, page 507.
a. Define the lattice, and list atoms in the basis, and their locations.
. Draw a crystal plan projected along [001]. Make sure all atoms are included in the unit
cell you are showing. Show your check for having one formula unit per cell.
c. Calculate the interatomic distances between Al and F(1), Al and F(2), K and F(1), and K
and F(2).
d. What is the bonding geometry around the Al-atom (drawing!). What is the bonding type
in this material? Justify your choice.
e. Rank the ionicity of the following compounds: LiF, TiO, SiC, CuBr, CaO, NiAl, ZnSe and
ZnO.
Problem 2: 30 points – 10 points per part
This table from Rohrer page 507 describes the C14 structure. Laves phases emerge because of
the trend of metallic structures to achieve the densest possible packing for dissimilar atomic
adii and many of the Laves structures have relatively large differences in atomic radii.
(a) How many formula units are in the unit cell (shown below) using the standard “atom
counting” procedure? Does this agree with the multiplicity given in the table above,
which is derived from the international tables for crystallography?
(b) In the panel below you see the 3D depiction of the C14 structure, and three projections
(ii) to (iv). Label the projections (index the plane on which the structure is projected)
using the 3 and 4 index notation for hexagonal lattices.
(c) Label the heights of all atoms NOT at z=0 or 1 in projection (ii). Lighter color means
smaller value of z.
View (i)
View (ii)
View (iii) View (iv)
Problem 3: 20 points
Open the ppt file and determine the 2D plane group for the pattern shown on slide 1. Please
mark all symmetry elements, and show them on slide 2.
Contact me if you do not have powerpoint, and I can send it in another format.
Problem 4: 20 points
A stereographic projection for the tetragonal lattice is shown below with the fourfold axis along
c indicated. Sketch and label all poles of the {101} family on the projection. It is helpful to draw
the 3D tetragonal lattice and mark a few of the planes – when are planes labeled as part of a
family of planes?