Material Chemistry 1st Exam
2003. 4.18
1.Why do you need to create a reciprocal space to understand the diffraction
pattern? Please use Bragg equation to illustrate this. (15%)
2.Crystal AB belongs to face center cubic (FCC) with a=5.0A: in one case A is
located at (0,0,0) and B at (1/2,0,0); in the other case A is at (0,0,0)
and B at (1/4,1/4,1/4). Please give in both cases
a)How many A and B atoms in the unit cell and what are they located?
b)What is the density of the crystal assuming the atomic weight of A and B
is 20 and 32 respectively.
c)What is the respective coordination number of A and B. (18%)
3.What types of information you can get from powder pattern (I vs Θ)? (7%)
4.What are K-, L- edge absorption standing for? Can you predict the edge
before doing the experiment? There are XANES and EXAFS part of spectra,
what are they and what information you can get from each part? (18%)
5.Compare with the molecular orbitals(MO) of an isolated molecule, the linear
chain of molecules give energy bands instead of orbitals, explain the
density of states(DOS) in such a chain structure. What will be the band gap
corresponding to your understanding of MO? (10%)
6.Suppose there is a linear chain of 3d transition metals, what do you expect
for the σ bond in terms of s- p- and d- orbitals? Illustrate the lowest
and the highest energy ones. (12%)
7.Normally we get magnetic property from a SQUID measurement where χ vs T is
obtained. How do you get effective magnetic moment (μeff) from this and
what the relationship between μeff and the electronic configuration of the
material? (10%)
8.Please use the equation, P=χ(1) E + χ(2) E^2 + χ(3) E^3 + ... , to
explain why the second-order nonlinear optical(NLO) material requires a
non-centrosymetrical arrangement of the composing molecules (5%). Please
illustrate five methods in aligning molecular materials to be suitable for
showing second-order nonlinear optical properties (5%).
9.What kind(s) of the display that is (are) most appropriate for OLEDs? (3%)
Please describe the advantage of OLED compared with LCD (7%)
Total:110%
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