Give examples of displacement defects in solids.

The defect produced due to the presence of extra cations at interstitial sites is called

While writing the formula of ferrous oxide,it is written as $(FeO)$,because it is

$A$ metallic solid undergoes Frenkel defect. Its original mass,volume and density are $M_0$,$V_0$ and $D_0$ respectively. After Frenkel defect the mass,volume and density are $M$,$V$ and $D$ respectively. The variations of $M$,$V$ and $D$ after Frenkel defect are

Which of the following statements are not correct?
$(A)$ Diode is a combination of $n$-type and $p$-type semiconductors.
$(B)$ Silicon or germanium is electron rich impurity.
$(C)$ Phosphorus and arsenic are electron deficient impurities.
$(D)$ Schottky defect decreases the density of the crystal.

Write a short note on Frenkel defect and Schottky defect.