LaTeX

No, it isn’t some kinky fun with rubber :-p

[math]

F(hkl) = \sum _{j} f _j (\theta) \cdot \exp[-8\pi^2U_j\sin^2 \frac {\theta} {\lambda^2}] \cdot \exp [2 \pi i (hx_j + ky_j + i z_j]

[/math]