4. Conclusions
The study of the vibrational entropy of solid solutions enables
the determination of the configurational entropy, if reliable enthalpic
and phase equilibrium data exist.
The high mobility of the Cu and Zn atoms in a-brass makes an
in situ calorimetric investigation of the ordering/disordering
processes possible.
The negative excess vibrational entropy of the Cu–Zn alloy can
be interpreted as follows: The end-member with the smaller volume
(i.e., Cu) is elastically much stiffer compared to the end-member
with the larger volume (i.e., Zn). The Cu atom will force,
therefore, the Zn atom to fit to its size in the solid solution. The
Zn bonds become, thus, much stiffer compared to the bonds in
the pure phase producing the negative excess heat capacity of mixing.
If the effect of the structural changes along the Cu–Zn binary is
taken into account, equation (1) gives a good estimate for this
system, too.
4. Conclusions
The study of the vibrational entropy of solid solutions enables
the determination of the configurational entropy, if reliable enthalpic
and phase equilibrium data exist.
The high mobility of the Cu and Zn atoms in a-brass makes an
in situ calorimetric investigation of the ordering/disordering
processes possible.
The negative excess vibrational entropy of the Cu–Zn alloy can
be interpreted as follows: The end-member with the smaller volume
(i.e., Cu) is elastically much stiffer compared to the end-member
with the larger volume (i.e., Zn). The Cu atom will force,
therefore, the Zn atom to fit to its size in the solid solution. The
Zn bonds become, thus, much stiffer compared to the bonds in
the pure phase producing the negative excess heat capacity of mixing.
If the effect of the structural changes along the Cu–Zn binary is
taken into account, equation (1) gives a good estimate for this
system, too.
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