Diamond structure can be considered as $\mathrm{ZnS}$ (Zinc blend) structure in which each ${\mathrm{Zn}}^{2+}$ in alternate tetrahedral void and ${\mathrm{S}}^2$ - in cubic close pack arrangement is replaced by one carbon atom. If $\mathrm{C}-\mathrm{C}$ covalent bond length in diamond is $1.5\stackrel{°}{\mathrm{A}}$, what is the edge length of diamond unit cell $(z=8)$.

Give the correct order of initials $\mathrm{T}$ (true) or $\mathrm{F}$ (False) for following statements :

I. In an anti-fluorite structure anions form $\mathrm{FCC}$ lattice and cations occupy all tetrahedral voids.

II. If the radius of cations and anions are $0.2\stackrel{°}{\mathrm{A}}$ and $0.95 \stackrel{°}{\mathrm{A}}$ then coordinate number of cation in the crystal is $4 .$

III. An atom/ion is transferred from a lattice site to an interstitial position in Frenkel defect.

IV. Density of crystal always increases due to substitutional impurity defect.