The compound Ni3Al is used to strengthen nickel based alloys used in high temperature gas turbine materials. The crystal structure of Ni3Al is a cube with Al atoms at the eight cube corners and Ni at all of the cube face centers.
(a) What is the Bravais lattice type for Ni3Al and
(b) What are the atom positions?
(a) Simple cubic because the Ni atoms at the face centered positions are not equivalent to the Al atoms at the corners. Therefore, only the corner atom positions are equivalent and this corresponds to the simple cubic lattice.
(b) Al-0,0,0 Assigning an atom to 0,0,0 also automatically places atoms at all of the equivalent 8 corners of the cube. Ni-1/2,1/2,0 0,1/2,1/2 1/2,0,1/2
Placing atoms at these three face centers also places an atom at the equivalent face on the other side of the unit cell. The other side of the unit cell is the equivalent face in the next unit cell.
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