let’s crake the question asked as follows –
explain how much portion of an atom located at corner and body centre of a cubic unit cell is part of its neighbouring unit cell ?
To solve this question you have to keep some key points in your mind –
Look at the structure of a body centred cubic unit cell , in this structure we can see that the atom present on corner of structure is shared by eight unit cell. On the other hand the atom present at centre of a cubic unit cell is not shared by any other unit cell.
give answer on the basis of these points as follows –
- A lattice point which is lying at the corner of a unit cell is shared equally by eight unit cell , it means one lattice point present at corner position is divided among 8 unit cell , hence only one-eighth (1/8) of each such point belongs to the given unit cell as shown in figure 1 above.
- On other hand the lattice point which is present at the position of body centred point belongs to entirely to one unit cell which is itself. it means the body centred point does not make any share with other unit cell. so the shared of body centred point is one.
in short answer –
how much portion of an atom located at corner = 1/8
how much portion of an atom located at body centre of a cubic unit cell = 1