Crystal Structure and Crystallography
Problem Session #2
Due date: 2016/03/23
1.
Calculate cation-anion radius ratio when the coordination number is 2, 3, 4, 6, and 8.
Assume that anion radii size is always larger than cation radii size and cation exists in the
interstitial site of anions. Consider the below schematic pictures.
2.
Draw a unit cell of NaCl crystal structure and index the positions of host atoms and
interstitial atoms. How many host atoms and interstitial atoms in a unit cell? In addition,
draw the (110) projection of this structure and identify the stacking sequence. From the
stacking sequence, can you identify that the interstitial atoms are located in the
octahedral sites of a FCC?
3.
Draw a unit cell of ZnS crystal structure (Sphalerite) and index the positions of host atoms
and interstitial atoms. How many host atoms and interstitial atoms in a unit cell? In
addition, draw the (110) projection of this structure and identify the stacking sequence.
From the stacking sequence, can you identify that the interstitial atoms are located in the
tetrahedral sites of a FCC?
4.
In the (110) projection of ZnS (Sphalerite), please indicate the plane where the Shockley
partial dislocation can move and indicate how the stacking sequence changes with one
dislocation movement.
5.
Draw a unit cell of ZnS crystal structure (Wurtzeit) and index the positions of host atoms
and interstitial atoms. How many host atoms and interstitial atoms in a unit cell? In
addition, draw the (11-20) projection of this structure and identify the stacking sequence.
From the stacking sequence, can you identify that the interstitial atoms are located in the
tetrahedral sites of a HCP?
6.
Describe the crystal structure of CaI2 and CdCl2 and explain the similarities and
differences of these two structures. Then, describe the stacking sequence of CdCl2 and
identify how many atoms exist in a unit cell.
7.
Please describe the corundum crystal structure (sapphire, Al2O3) and identify the stacking
sequence of this structure. How many atoms in a unit cell?
8.
Please find out Bixbite crystal structure (for instance, In2O3 is known to form this
structure) in the web-site and describe how the atoms are arranged in a unit cell. How
many atoms are in a unit cell?
9.
Index the position of atoms located in Spinel crystal structure. Note that there are 32
oxygen atoms, 16 atoms in an octahedral site and 8 atoms in a tetrahedral site. You have
to consult the drawings in the class note.