Question

For a cubic unit cell, the dashed arrow in which of the following figures represents the direction [220] ?

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is C

To determine the direction [220] in a cubic unit cell, we need to understand what this notation signifies in terms of crystallographic directions.

The direction [220] is expressed in terms of the Miller indices, which represent directions in the crystal lattice. The process to interpret this direction is as follows:

1. Start from the origin (0,0,0).
2. The direction indices [220] mean:
   • Move 2 units along the x-axis.
   • Move 2 units along the y-axis.
   • Move 0 units along the z-axis.
3. This indicates movement within the xy-plane, without moving up or down along the z-axis.

Now, let us examine the options given to find the image depicting this directional movement:

The correct option is the third image (Cube XYZ 3), as it clearly shows a vector pointing within the xy-plane, moving both in the positive x and positive y directions while staying constant along the z-axis.

Hence, the direction [220] is accurately represented by the dashed arrow in the Cube XYZ 3.