How Is the CsCl Unit Cell Described Using Its Primitive Cell and Basis?

[Lemenks]

Homework Statement

CsCl has a BCC unit cell containing 2 atoms, Cs in the origin of the cell and Cl at the centre of the cell. Describe the CsCl unit cell in terms of its primitive cell+basis.

Homework Equations

R = n1a1 + n2a2 + n3a3 ~ R is the vector which relates one point of the lattice to any other.

The Attempt at a Solution

R = n1a1 + n2a2 + n3a3,
Where Cs is at the point (0,0,0) and Cl is at the point (1/2,1/2,1/2)

My issue is mostly with the terminology - I am not really sure what the question is asking. I know that either ion can be described with a SC lattice and together they make a BCC lattice. I don't really know how to answer this.

 

[ehild]

It the Cs and Cl ions were identical spheres, the unit cell would look like as BCC . But they are different, so it is not BCC but a primitive cell with a basis. What kind of cell and what is the basis?

ehild

 

[Lemenks]

Emm, I think its a SC primitive cell with a two point basis, where Cs is at the point (0,0,0) and Cl is at the point (1/2,1/2,1/2).

 

[ehild]

Correct :)