Solidified gases and Bloch functions.

[Wicked85]

Hi! I have two multiple choice question which I'm having trouble solving.

1) Why do all elements (except rare gas atoms) seldomly close pack as much as the rare gas atoms although they attract each other much more.
i. Too much attraction deforms the crystal structure
ii. It is due to temperature effect. Indeed at 0K all materials close pack.
iii. Chemical bonding cannot be reduced to pairwise attractions
iiii. It's a surface effect: the surface applies an inwards pressure, which is minimized by the actual crystal structure.

2)For an electron in a crystal, which of the following statements are true?
i. The Bloch function computed at two different k's in the Brillouin zone are orthogonal.
ii. The periodic part of the Bloch functions computed at two different k points in the Brillouin zone are orthogonal.
iii. Two Bloch functions computed at two different k points in the Brillouin zone differ just in the phase factor.
iiii. All Bloch functions can be taken to be periodic for an appropriate choice of the phase.

I think that (ii) is the correct answer in question 1. And (i) and (iii) are correct in question 2. Any thoughts or comments on that? :)
/Simon

 

[kanato]

Your answer to 1 is definitely wrong.
For 2, I might say that you are half right, although I'm not sure exactly what they mean by option iiii.

You should state why you think those answers are right, and then we can have discussion that leads to getting the correct answers. Otherwise I just tell you that your answers are right or wrong, or give you the right answers.