# How to determine interplanar spacing for BCC/FCC crystals?

I have a query as to how interplanar spacing in fcc and bcc can be determined. In line with the known formula,

$$d_{hkl} = \frac{a}{\sqrt{h^2+k^2+l^2}}$$

for a crystal with Miller indices (1 1 0), if the crystal is scc/bcc then the formula holds good! But for fcc, it does not! According to the formula, the spacing is $$\frac{a}{\sqrt{2}}$$, but in practical observation it is $$\frac{a}{2\sqrt{2}}$$.

I searched for a distinct formula on the internet to satisfy the fcc case, but I failed! I read some books, looked at some questions, and the author uses the ordinary formula to solve the questions.

I'm confused! Help me to understand where I'm incorrect!

That's the spacing for (2,2,0) and not (110). For an FCC crystal with identical atoms the (110) has zero structure factor and does not show up.

• Can you explain the second part more clearly ? Sep 8, 2019 at 6:17
• This video will help you understand where I am confused youtu.be/VycyIzulE68 see the 111 spacing in this video! Is that correct? Sep 8, 2019 at 6:29