MATLS 1M03 Chapter 4: Chapter 4.pdf

• School: McMaster University
• Department: Materials Science and Engineering
• Course: MATLS 1M03
• Professor: Hatem Zurob

Document Summary

3: vacancies:a normally occupied lattice site from which an atom or ion is missing, thermodynamics says that there is an equilibrium number of vacancies: Why is this number of vacancies thermodynamically stable? exp (depending on units of q) Introduction of a small number of vacancies lower the free energy . (cid:4666)not covered in textbook(cid:4667) Entropy (cid:4666)s(cid:4667) is the key: a crystal only has one perfect configuration. Configurational entropy is zero: vacancies (cid:4666)on the other hand(cid:4667) give rise to many configurations. The equilibrium vacancy concentration increases by atom motion from the crystal to the surface, where they join the island. Island grows/shrinks to maintain equil. vancancy conc. in the bulk. (click to play) 8: a solute atom is defined as an atom which different from the host atoms (cid:4666)e. g. cu atom in ni(cid:4667). Sometimes we refer to solutes as impurities: solid solubility. 9: atomic size factor, crystal structure, electronegativity, valences. The tale of the engineering student and the philosopher.