$\large \vec{k}=u\vec{b}_1+v\vec{b}_2+w\vec{b}_3\,:\,(u,v,w)$  Symmetry points $(u,v,w)$  $[k_x,k_y,k_z]$  $\Gamma:\,(0,0,0)$   $[0,0,0]$  $X:\,(\frac{1}{2},0,0)$   $[\frac{\pi}{a},\frac{\pi}{a},0]$   $Z:\, (\frac{1}{2},\frac{1}{2},-\frac{1}{2})$   $[\frac{2\pi}{a},0,0]$   $N:\, (0,\frac{1}{2},0)$   $[\frac{\pi}{a},0,\frac{\pi}{c}]$   $P:\, (\frac{1}{4},\frac{1}{4},\frac{1}{4})$   $[\frac{\pi}{a},\frac{\pi}{a},\frac{\pi}{c}]$    $\overline{\Gamma X} = \frac{\sqrt{2}\pi}{a}$ $\overline{\Gamma Z} = \frac{2\pi}{a}$ $\overline{\Gamma N} = \frac{\pi}{ac}\sqrt{a^2+c^2}$ $\overline{\Gamma P} = \frac{\pi}{ac}\sqrt{a^2+2c^2}$    Symmetry lines   $\Delta :\,(v,0,0)$ $0\lt v\lt\frac{1}{2}$   $\Sigma :\,(v,v,-v)$ $0\lt v\lt\frac{1}{2}$   $Y :\,(\frac{1}{2},v,-v)$ $0\lt v\lt\frac{1}{2}$   $\Lambda :\,(-v,v,v)$ $0\lt v\lt\frac{1}{4}+\frac{c^2}{a^2}$   $W :\,(\frac{1}{2}-v,v,v)$ $0\lt v\lt\frac{1}{4}$   $Q :\,(v,\frac{1}{2}-v,v)$ $0\lt v\lt\frac{1}{4}$

The real space and reciprocal space primitive translation vectors are:

$\large \vec{a}_1 = \frac{a}{2}(\hat{x}+\hat{y})-\frac{c}{2}\hat{z}$  $\large \vec{a}_2 = \frac{a}{2}(\hat{x}-\hat{y})+\frac{c}{2}\hat{z}$  $\large \vec{a}_3 = \frac{a}{2}(-\hat{x}+\hat{y})+\frac{c}{2}\hat{z}$,

$\large \vec{b}_1 = \frac{2\pi}{a}(\hat{k_x}+\hat{k_y})$  $\large \vec{b}_2 =\frac{2\pi}{a}\hat{k_x}+\frac{2\pi}{c}\hat{k_z}$  $\large \vec{b}_3 = \frac{2\pi}{a}\hat{k_y}+\frac{2\pi}{c}\hat{k_z}$.

• Cut-out pattern to make a paper model of the body centered tetragonal Brillouin zone.