Radii of A+ and that of X- and Y- have been given as A+= 1.00 pm, X- =1.00 pm, Y- = 2.00 pm.Thus, ratio of volumes of AX and AY unit cells is

Ratio of r+/r_ will decide the type of unit cell.For AXrA+rX−=11=1.0 hence, AX has bcc structure. ∴2rA++rX−=a3a=23rA++rX−=2×23=43PM∴ Volume (AX)=a3=433=6433 For AY rA+rY−=12=0.5Thus, octahedral or square planar structure.r=a2∴a=2r=2rA++rY−=2(1+2)=6pm  Volume (AY)=a3=216pm3 ∴ Ratio = Volume (AX) Volume (AY)=6433×216=0.057