In the unit cell of spalerite, Zn2+ ions occupy half of the tetrahedral holes in a face-centered cubic lattice of S2- ions. The number of ZnS formula units in the unit cell is:
As this type of question is difficult to answer without images, just go to this site:
http://www.everyscience.com/Chemistry/Inorganic/Io…
You will find the sphalerite structure and you will see that there are 4 units of ZnS in each unit cell.
You get this by counting sulfur atoms:
You have 8 that contribute 1/8 of an atom and 6 that take up 1/2 for a total of 4.
The 4 zinc atoms are completely in the cell.
Zns unit cell
Bragg’s equation n? = 2dsin? the locus n is an integer, ? is the wavelength of the incident wave, d is the spacing between the planes inside the atomic lattice and ? is the attitude between the incident ray and the scattering planes. art in Å 2×0.7873 =2dsin(11.57) d = 2×0.7873/2sin(11.57) = 3.925 Å Diagonal face = 4rPt = ?2a rPt = ?(2)a/4 = un million. 39 Å on: 138 h