HCP crystal is made of A ions and B ions are arranged in 2/3rd of octahedral voids. The formula of the unit cell is?

Dear Student,

Please find below the solution to the asked query:

HCP structure has  6 atoms present per unit cell.
A occupies HCP structure, therefore A= 6

Also there are 6 octahedral voids in HCP arrangement.
according to the question,
B occupies 2/3of voids 
so 2/3 *6 = 4

thus the simplest ratio is A:B = 6:4
                                         A:B = 3:2
Thus the formula is A₃B₂