Empty lattice approximation for a simple orthorhombic crystal

$\Large \frac{E}{\frac{\hbar^2}{2ma^2}}$

a/b:   a/c:   

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

  Symmetry points  ($u,v,w$)  [$k_x,k_y,k_z$]
  Γ: (0,0,0)    [0,0,0]
  X: (1/2,0,0)    [π/a,0,0]
  Y: (0,1/2,0)    [0,π/b,0]
  Z: (0,0,1/2)    [0,0,π/c]
  T: (0,1/2,1/2)    [0,π/b,π/c]
  U: (1/2,0,1/2)    [π/a,0,π/c]
  S: (1/2,1/2,0)    [π/a,π/b,0]
  R: (1/2,1/2,1/2)    [π/a,π/b,π/c]
\[ \begin{equation} \vec{b}_1=\frac{2\pi}{a}\hat{k}_x,\hspace{1cm} \vec{b}_2=\frac{2\pi}{b}\hat{k}_y,\hspace{1cm} \vec{b}_3=\frac{2\pi}{c}\hat{k}_z. \end{equation} \]