Atoms of element $B$ form $hcp$ lattice and those of the element $A$ occupy $2/3$ of tetrahedral voids. What is the formula of the compound formed by the elements $A$ and $B$?

$A$ binary solid has a zinc blende structure with $B$ ions constituting the lattice and $A$ ions occupying $25\%$ of the tetrahedral holes. The formula of the solid is:

In a face-centred cubic arrangement of $A$ and $B$ atoms,$A$ atoms are at the corners of the unit cell and $B$ atoms are at the face centres. If one of the $A$ atoms is missing from one corner of the unit cell,what is the simplest formula of the compound?

What are the percentages of empty space in a cubic close-packed $(CCP)$ structure and a body-centered cubic $(BCC)$ structure,respectively?

If the unit cell of a mineral has cubic close packed $(ccp)$ array of oxygen atoms with $m$ fraction of octahedral holes occupied by aluminium ions and $n$ fraction of tetrahedral holes occupied by magnesium ions,$m$ and $n$,respectively,are

Potassium hexachloroplatinate $(K_2PtCl_6)$ adopts an antifluorite crystal structure. The corners and face centers of the cubic unit cell are occupied by :-