If a plane passes through the origin, which step is performed first according to the described Miller index procedure?

• A. Move axis to the nearest plane
• B. Find point plane intercepts axis
• C. Take reciprocal
• D. Encase in parentheses

Answer: (A)

When identifying Miller indices, the plane’s intercepts with the crystallographic axes must be finite. A plane that passes through the origin has intercepts at infinity, so you can’t directly read off h, k, and l.

Therefore the first action in the described procedure is to translate the plane (or equivalently shift the coordinate axes) so that it intersects all three axes at finite distances. This is described as moving the axis to the nearest plane.

Once you have finite intercepts, you take the reciprocals of those intercepts to obtain h, k, and l. Then you clear any fractions to get the smallest set of integers, and finally enclose them in parentheses to denote the Miller indices.

So the initial step is to reposition so the plane no longer passes through the origin, enabling finite intercepts and the subsequent reciprocal step.