Vibrational Entropy in Binary AxB1-x Alloy

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In summary, the conversation discusses the validity of neglecting the contribution of vibrational entropy in the entropy of mixing for a binary AxB1-x alloy. Factors such as crystal structure and atomic weights are considered, with an example of the GaN-GaP pseudobinary system being mentioned. It is concluded that for small values of x and similar local chemical environments, it may be reasonable to neglect the change in vibrational entropy.
  • #1
knghrts17
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Hello all,


I am looking at the entropy of mixing for a binary AxB1-x alloy and I was wondering, when is it a valid assumption to neglect the contribution arising from the change in vibrational entropy between the mixed and the unmixed state.


Thanks in advance!
 
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  • #2
Does the crystal structure change? How large is x? For small x it is probably reasonable, but might not be if A and B are very different atomic weights.
 
  • #3
Kanato,

As an example, consider GaN-GaP pseudobinary system in the wurtzite phase. In pure GaN, GaP both N and P atoms are terahedrally coordinated to Ga. In a mixed state, these atoms have the same local chemical environment. In that case would it be a valid assumption to neglect the change in vibrational entropy?
 

1. What is vibrational entropy in a binary AxB1-x alloy?

Vibrational entropy in a binary AxB1-x alloy refers to the measure of disorder or randomness in the vibrations of atoms within the alloy. It is a thermodynamic quantity that takes into account the different arrangements of atoms and their corresponding vibrational energies in the alloy.

2. How is vibrational entropy calculated in a binary AxB1-x alloy?

Vibrational entropy in a binary AxB1-x alloy is calculated using statistical thermodynamics methods, such as the Debye model or the Einstein model. These models take into account the vibrational frequencies and energies of the atoms in the alloy, as well as their relative compositions.

3. What factors affect vibrational entropy in a binary AxB1-x alloy?

The main factors that affect vibrational entropy in a binary AxB1-x alloy are the composition of the alloy, the types of atoms present, and the temperature. As the composition and types of atoms change, so do the vibrational frequencies and energies, which in turn affect the overall vibrational entropy. Additionally, as the temperature increases, the vibrational entropy also increases.

4. Why is vibrational entropy important in the study of binary AxB1-x alloys?

Vibrational entropy is an important quantity to consider in the study of binary AxB1-x alloys because it provides insight into the structural and thermodynamic properties of the alloy. It can help predict the behavior of the alloy at different temperatures and compositions, as well as provide information on phase transitions and stability.

5. How does vibrational entropy relate to other thermodynamic properties in binary AxB1-x alloys?

Vibrational entropy is closely related to other thermodynamic properties in binary AxB1-x alloys, such as heat capacity and free energy. It is often used in conjunction with these properties to fully understand the behavior of the alloy and make predictions about its properties. Additionally, changes in vibrational entropy can affect the values of other thermodynamic properties, and vice versa.

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