Vibrational Entropy in Binary AxB1-x Alloy

[knghrts17]

Hello all,


I am looking at the entropy of mixing for a binary A_xB_1-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!

 

[kanato]

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.

 

[knghrts17]

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?