in a solid AB having the NACL structure A atoms occupy the corners of the cubic unit cell. if all the face centred atoms along one of the axes are removed, then the resultant stiochiometry of the solid is show my steps

Asked by Farooq Ahmad | 13th Apr, 2016, 08:04: PM

Expert Answer:

According to the structure of NaCl 
Here, 'A'  will occupy 8 corners of  cubic unit cell which will contribute 1/8 each to the cube
therefore 8*1/8 = 1
and 6 face centered atoms will contribute 1/2 to the cube
hence 6x1/2=3
Therefore total contribution of atom'A' is  3+1=4
Now B occupies octahedral voids (NaCl structure)  which contributes 1/4
therefore 1+12x1/4 = 4
So the formula is A A4B4 or AB
Now  we are removing all  face centered atoms along one axis
so the number of atoms removed from cube are 2
so contribution from 'A' remains 8x1/8(corner atoms) + 4x1/2(facecentered atoms) = 3
so the resultant becomes A3B4

Answered by Vaibhav Chavan | 15th Apr, 2016, 09:31: AM