Q1. Answer in brief:
- i.) List the symmetries of the C6H6 molecule. (50 words)
- ii.) Draw the first Brillouin zone for a 2D oblique reciprocal lattice. (50 words)
- iii.) What are the advantages of the neutron diffraction method? (50 words)
- iv.) Write down the electronic configuration of the Si atom. What type of bonding would you expect to find in Si? (50 words)
- V.) The electronic and lattice heat capacities for copper at 0.01 K are 5.04×10-6 J/(kmole-K) and 4.60×10-11 J/(kmole-K) respectively. What do you conclude from these magnitudes? (50 words)
- vi.) Is the following statement true for vibrations of a chain of two different types of atoms: "At the centre of the Brillouin zone, the frequency of the optical branch is less than the frequency of the acoustic branch”? Explain. (50 words)
- vii.) The Fermi energy for silver is 5.48 eV. Which of the following is true : (a) the density of energy states is greater at 2 eV (b) the density of energy states is greater at 6 eV or (c) the density of energy states is same near both energies? (50 words)
- viii.) What is the probability that a donor atom at energy En is ionized ? (50 words)
- ix.) In which of the following ions do you expect angular momentum quenching and why: Ti³⁺, Gd³⁺, Ni²⁺ (50 words)
- x.) What is the function of the quartz crystal used in a digital watch? (50 words)
Key Points:
- C6H6 has D6h point group with C6, C2, σh, σv, σd, and inversion symmetries.
- First Brillouin zone for 2D oblique lattice is a parallelogram.
- Neutron diffraction excels in locating light atoms, magnetic structures, and inelastic scattering.
- Silicon has 1s²2s²2p⁶3s²3p² configuration and forms strong covalent bonds.
Answer: