homeworks 2015 QNU (1)

Homework 1 Illustrate the difference between the symmetry elements 6 1 and by completing their symmetry figure below.. Homework 2 Determine the point group Schoenfliess nomenclature of t

Homework 1

Illustrate the difference between the symmetry elements 6 1 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?