- #1

etotheipi

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Given a crystal basis ##\{\vec{a}, \vec{b}, \vec{c} \}##, the two lattice vectors ##\vec{r}_1 = u_1 \vec{a} + u_2 \vec{b} + u_3 \vec{c}## and ##\vec{r}_2 = 2u_1\vec{a} + 2u_2 \vec{b} + 2u_3 \vec{c}## both obviously point in the same direction whilst ##\vec{r}_2## is twice as long as ##\vec{r}_1##. However, some people drop the common factors and index both as ##[111]##, whilst others seem to keep the common factors and index them as ##[111]## and ##2[111]## respectively.

So, regarding this [...] notation, does it represent a direction or a vector?

So, regarding this [...] notation, does it represent a direction or a vector?

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