Despite the approximations in this model, several of the predictions are nonetheless a reasonable qualitative match to the experimental measurements in Ref. . The measurements on the Bi2(S,Se)3 system indicate that Bi2S2Se and Bi2SSe2, which both adopt the Pnma phase, have a lower 𝜅 latt than Bi2S3. Similarly, the measurements on Bi2(Se,Te)3 predict a minimum in the 𝜅 latt for Bi2Se0.3Te2.7, a reduced 𝜅 latt for Bi2SeTe2, and an increased 𝜅 latt for Bi2Se2Te compared to Bi2Te3. The interpolation predicts the minimum to occur at Bi2Se0.15Te0.85, which is between the two compositions measured to have 𝜅 latt lower than Bi2Te3, and the model also predicts an increase in 𝜅 latt above the Bi2Te3 endpoint at Bi2Se2Te (𝑥 = 1/3). We therefore conclude that this model can make useful qualitative, if not quantitative, predictions.