1.(10pts) For a BCC crystal, which has higher surface energy (100) or (110) ? Why? 2.(10pts)Describe a twin and twin boundary. What is the difference between a Mechanical twins and annealing twins? 3. (10pts) Why do we prefer to use semiconductor crystals with the lowest number of dislocations? 4. (10pts) Is it easier to fit a interstitial atom above or below the dislocation line shown below? 5. (10pts) Calculate the length of the Burgers vector for FCC silver with atomic radius of 0.40862nm