1. What is the angle between the bonds in the diamond lattice?
2. In a simple cubic lattice, what is the angle among the following planes?
(a) (100) and (110), b) (100) and (111)?
3. In order to modify the properties of a pure germanium sample, it is uniformly doped by boron forming substitution impurities such that 3×10^5% of germanium atoms are replaced by boron ones. What is the concentration of boron atoms in the sample? What is the fraction by weight of boron?