In the Point to Crystallographic Direction method, what is the second step after obtaining fractions?

• A. Divide by highest number to get fractions
• B. Do head-tail calculation to get head and tail points
• C. Put in brackets and dash negative signs
• D. Multiply to clear fractions

Answer: (B)

Once you have the fractional coordinates for the two lattice points, you need to form the direction vector between them. This is done with a head-tail calculation: subtract the tail point from the head point to obtain the differences Δx, Δy, and Δz. Those differences give the direction in fractional form. After this, you would typically clear any fractions by multiplying by the least common multiple of the denominators and then reduce to the smallest integer components to get the Miller indices [uvw]. So the second step is the head-tail calculation to get the head and tail points, i.e., the direction vector.