# homeworks 2015 QNU (1)

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Homework 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 Determine the point group (Schoenfliess nomenclature) of the following molecules CH4, CH3Cl, CH2Cl2, CHCl3, CCl4 dichlorobenzene (three isomers) C2H2 and C2HF ethane (eclipsed) ethane (staggered) CH2=C=CH2 (allene) Hints: - use flow chart from lecture Homework Draw the symmetry elements for the drawings given Add the unit cell, determine the plane group and draw the asymmetric unit Homework 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 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 (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, 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 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?
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