A Guide to Physics Problems. Part 2. Thermodynamics, Statistical Physics, and Quantum Mechanics

THERMODYNAMICS AND STATISTICAL PHYSICS 227

be used as an approximation). The vacancies and interstices then can be

distributed in and ways,respectively:

The total number of possible configurations of the system, is given by

The entropy, S, may be written

Using Stirling’s formula

we obtain,from (S.4.99.3),

Using (S.4.99.5) and the fact that the total energy of thesystem
we have

or