Which stoichiometric defect in crystals increses the density a solid?

Explanation

**Step-by-Step Solution:**

1. **Understanding Stoichiometric Defects:**
- Stoichiometric defects are imperfections in the crystal lattice that do not change the overall composition of the crystal. They can be classified into different types, such as vacancies, interstitials, and others.

2. **Identifying the Effect on Density:**
- The density of a solid is defined as its mass per unit volume. For the density to increase, there must be an increase in mass without a significant increase in volume.

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