In a hypothetical solid, $\mathrm{C}$ atoms form $\mathrm{CCP}$ lattice with $\mathrm{A}$ atoms are occupying all the tetrahedral voids ($\mathrm{TV}$) and $\mathrm{B}$ atoms are occupying all the octahedral voids ($\mathrm{OV}$). $\mathrm{A}$ and $\mathrm{B}$ atoms are of the appropriate size such that there is no distortion in the $\mathrm{CCP}$ lattice. Now, if a plane is cut (as shown), then type of voids and their numbers which are present at the cross section would be

  

Consider the bcc unit cells of the solids $1$ and $2$ with the position of atoms as shown below. The radius of atom $\mathrm{B}\mathrm{ }$ is twice that of atom $\mathrm{A}.$ The unit cell edge length is $50\mathrm{ }\mathrm{\%}$ more in solid $2$ than in $1$ . What is the approximate packing efficiency in solid $2$ ?

An element crystallises in a face–centred cubic (fcc) unit cell with cell edge a. The distance between the centres of two nearest octahedral voids in the crystal lattice is:

The vacant space in bcc lattice unit cell is:

The packing efficiency of the face centered cubic (FCC), body centered cubic (BCC) and simple/primitive cubic (PC) lattices follows the order