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Negative indices

unit cell

 

To index this plane it is useful to use a different corner of the unit cell as the point of reference.

Go along the positive x and z axes to find those intercepts.

Then go backwards along the negative y-axis, to get a negative intercept.

unit cell z x -y c/2 a/1 -b/1

 

Instead of using a minus sign, we use an 'overbar' to denote a negative index. This gives a Miller Index of:

(112)

This reads as "one, bar one, two".

unit cell z x -y
          
unit cell z x -y