ABSTRACT
We now determine the configurational entropy S of the crystal with vacancies. The number of possibilities to form n vacancies in an N atom crystal is
(8.3)
Ω= − N
N n n !
( )! !
We divide by n! because it does not matter in which sequence we remove the n identical atoms (Reif, 1965). The entropy is proportional to the logarithm of the number of possible arrangements:
(8.4)S= kB lnΩ
where kB is the Boltzmann constant. In addition, there are some subtle changes in entropy that arise primarily from vibrational modes. The term nSV denotes the change in vibrational entropy that is caused by the introduction of n vacancies.
