Empty lattice approximation for a body centered tetragonal crystal

\(\Large \frac{a\omega}{c}\)

a/c:   

$\large \vec{k}=u\vec{b}_1+v\vec{b}_2+w\vec{b}_3\,:\,(u,v,w)$

 Symmetry points $(u,v,w)$ $[k_x,k_y,k_z]$
 $\Gamma:\,(0,0,0)$  $[0,0,0]$
 $X:\,(\frac{1}{2},0,0)$  $[\frac{\pi}{a},\frac{\pi}{a},0]$ 
 $Z:\, (\frac{1}{2},\frac{1}{2},-\frac{1}{2})$  $[\frac{2\pi}{a},0,0]$ 
 $N:\, (0,\frac{1}{2},0)$  $[\frac{\pi}{a},0,\frac{\pi}{c}]$ 
 $P:\, (\frac{1}{4},\frac{1}{4},\frac{1}{4})$  $[\frac{\pi}{a},\frac{\pi}{a},\frac{\pi}{c}]$ 
 

$\overline{\Gamma X} = \frac{\sqrt{2}\pi}{a}$

$\overline{\Gamma Z} = \frac{2\pi}{a}$

$\overline{\Gamma N} = \frac{\pi}{ac}\sqrt{a^2+c^2}$

$\overline{\Gamma P} = \frac{\pi}{ac}\sqrt{a^2+2c^2}$

The real space and reciprocal space primitive translation vectors are:

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

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