Question

Three atoms A, B and C crystallize in a cubic
solid lattice where A atoms are present at the body
centre, B atoms are present at the edge centre as
well as at the comers of the cube and C atoms are
present at the face centres of the cube. Now if all
the atoms are removed from the two 4-fold axis
and the one 2-fold axis passing through the cube,
then the formula of the compound is


I want the meaning of the 4 fold axis and 2 fold axis ​

Answer 1

Answer:

Removed atoms are 2B , 4C and 1A.

A=1 as the 2 fold axis passes through the center hence A=1 - 1 = 0.

For B, 2 atoms of the B are removed which are opposite to edge center.

As B, present at corners as well the 12 - 2 = 10 atoms of B.

At corners, B = 10*1/4 = 5/2.

At edge, B = 8 * 1/8= 1 .

Total B atoms = 1 + 5/2 = 7/2.

For C, 4 atoms are removed = 6 - 4 = 2 atoms left.

By sharing C=1/2 * 2 = 1.

A0 : B7/2 : C1 = B7C2 is the formulae.