Engineering Board Exam Reviewer · Engineering Materials · hard

Copper has 8.0 × 1028 atoms/m³ and a vacancy formation energy of 0.9 eV/atom. How many vacancies per cubic meter exist at 1000 ° C? (k = 8.62 × 10-5 eV/K)

1. 2.34 × 1024 m-3
2. 2.19 × 1025 m-3
3. 2.19 × 1027 m-3
4. 6.56 × 1029 m-3

Answer

B. 2.19 × 1025 m-3

Solution

Nv = N (-Qv/kT) = 8.0 × 1028 [-0.9/(8.62 × 10-5 × 1273)] = 2.19 × 1025 vacancies/m³.

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