Vibrational Entropy in Binary AxB1-x Alloy

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The discussion focuses on the vibrational entropy of mixing in binary AxB1-x alloys, specifically questioning when it is valid to neglect the contribution from vibrational entropy changes between mixed and unmixed states. Participants highlight that for small values of x, particularly when A and B have similar atomic weights, this assumption may hold true. The example of the GaN-GaP pseudobinary system in the wurtzite phase illustrates that when both N and P atoms are tetrahedrally coordinated to Ga, neglecting vibrational entropy changes may be justified.

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  • Basic concepts of atomic coordination in materials science
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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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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.
 
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?
 

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