In an ccp arrangement of A and B atoms ,A is present at the corners as well as face centres of the unit cell and B at its edge centres as well as body centres..If one atom of A is missing from its position at the corners,what is the formula of the compound?
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A: in one cubic cell: 8 corners * 1/8 + 1/2 * 6 faces = 4 atoms
B : 1/4 * 12 edges + 1 center = 4 atoms.
So the formula for ccp arrangement with no atoms missing: A4 B4
1)
If one atom of A is missing from the face center :
8 corners * 1/8 + 1/2 * 5 faces = 7/2 in one cell
So Formula is: A_7/2 B_4 or A7 B8
2) If one atom of A is missing from the corner of a cell:
we have 7/8 + 1/2*6 = 31/8 atoms in a cell.
Formula : A_31/8 B_4 or A31 B32
B : 1/4 * 12 edges + 1 center = 4 atoms.
So the formula for ccp arrangement with no atoms missing: A4 B4
1)
If one atom of A is missing from the face center :
8 corners * 1/8 + 1/2 * 5 faces = 7/2 in one cell
So Formula is: A_7/2 B_4 or A7 B8
2) If one atom of A is missing from the corner of a cell:
we have 7/8 + 1/2*6 = 31/8 atoms in a cell.
Formula : A_31/8 B_4 or A31 B32
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