P$3(10$ points$)$

Sketch the $(0001)$ plane in HCP and calculate the planar atomic density in atoms per

square millimeter, atoms $\frac{?}{m{m}^2}$ for the plane in HCP beryllium, which has a lattice param$-$

eter of $a=0\mathrm{.}22856nm$ and a $c$ constant of $0\mathrm{.}35832$ nm $.$

P$4(10$ points$)$

Calculate the linear atomic density in atoms per millimeter, atoms $\frac{?}{m{m}^2}$ for the following

directions in BCC vanadium, which has a lattice parameter of $0\mathrm{.}3039$ nm : $($a$)[100],($b$)$

$[110],$ and $($c$)[111].$