homeworks 2015 QNU (1)
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Homework 1
Illustrate the difference between the symmetry elements 61 and
by completing their symmetry figure below.
Hints:
- remember to rotate always counterclockwise
- don't forget to add a comma for inversion
Homework 2
Determine the point group (Schoenfliess nomenclature) of the following
molecules.
1. CH4, CH3Cl, CH2Cl2, CHCl3, CCl4
2. dichlorobenzene (three isomers)
3. C2H2 and C2HF
4. ethane (eclipsed)
5. ethane (staggered)
6. CH2=C=CH2 (allene)
Hints:
- use flow chart from lecture 2
Homework 3
Draw the symmetry elements for the drawings given. Add the unit cell, determine the plane
group and draw the asymmetric unit.
Homework 4
1. Complete the symmetry figure by adding the equivalent positions.
2. Complete the symmetry figure by adding the equivalent positions.
Give the name of this space group, the coordinates of the equivalent positions, the
multiplicity and the asymmetric unit.
(a)
(b)
(c)
Homework 5
The Green Fluorescent Protein crystallises in the space group P41212 with unit
cell a = b = 89.23, c = 119.77 Å, α = β = = 90°. Calculate the diffraction angle 2
for reflection (10,0,0) when Cu Kα radiation ( = 1.54 Å) is used for the data
collection.
Homework 6
(a)
Sodium chloride NaCl crystallises in a cubic unit cell with a = 5.63 Å and atoms
at the following positions:
Calculate the structure factor for the reflections (111) and (210) using the
formulas:
Use the symbols fNa and fCl for the scattering factors of Na and Cl.
(b)
Cesium iodide CsI crystallises in a cubic unit cell with atoms at the following
positions:
Cs
0, 0, 0
I
1/2, 1/2, 1/2
Predict the intensities of the reflections 0,0,1 and 0,0,2 as a function of the
scattering factors of both atoms.
Homework 7
Crystal data of euphenyl iodoacetate:
C32H53IO2, space group P21, Z=2
a = 7;26
b = 11.55
c = 19.22 Å
α = 90.0
β = 94.07
= 90. 0°
Explain the Harker section P(u, 1/2, w).
Determine x and z of the iodine atoms in the unit cell.
Determine the sign of the following reflections:
The scattering factors are as follows:
Which phases are correct?
