# Miller bravais indices

by aaaa202
Tags: bravais, indices, miller
 P: 1,005 There are four miller indices (hklj) for the hexagonal lattice, the third being redudant: l=-(h+k) (1) Given the basis vectors a1,a2,a3 I can certainly see that: a3=-(a1+a2) But how does this immidiatly lead me to the relation (1) between the miller indices?
 Sci Advisor P: 3,630 Spontaneously, I don't know the answer, but I think it is relatively easy to work out. Have you tried? If you really encounter problems, we all are willing to help you.
 P: 746 The redundancy in coordinate implies the relationship
P: 1,988
Miller bravais indices

 Quote by aaaa202 Given the basis vectors a1,a2,a3 I can certainly see that: a3=-(a1+a2) But how does this immidiatly lead me to the relation (1) between the miller indices?
How do you define these basis vectors? Is a3 in the same plane as a1 and a2?
 P: 1,005 Yes they are are all with a 60 degree angle relative to each other.
 P: 1,005 The problem is how exactly to relate the miller indices given (-a1+a2)=a3. After all miller indices for a plane are obtained as inverses of the coordinates for the intersection of the lattice vectors with the plabe.
 P: 1,988 Oh, so these are the a1,a2,a3 in the system with four indices. You have and a4 as well. Right? Sorry, I was confused.
 P: 1,005 yes exactly, 3 vectors in the hexagonal plane, one in the c-direction
 P: 673 Hint: Miller indices refer to a point in reciprocal space, hence you have to construct the reciprocal space basis vectors. G = H a* + K b* + L c*(for the "normal" 3 Miller indices).

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