Table 2 The Longitudinal and transverse average group velocities (vi in km/s), Debye temperatures (θi in K), and Grüneisen parameter \({\mathop{{\rm{\gamma }}}\limits^{-}}_{i}\) for each acoustic phonons.

From: Theoretical predicted high-thermal-conductivity cubic Si3N4 and Ge3N4: promising substrate materials for high-power electronic devices

 

v LA

v TA/TA'

θ LA

θ TA'

θ TA

\(\mathop{{\rm{\gamma }}}\limits^{-}\) LA

\(\mathop{{\rm{\gamma }}}\limits^{-}\) TA'

\(\mathop{{\rm{\gamma }}}\limits^{-}\) TA

γ-Si3N4

11.95

9.04

600

484

434

1.43

1.10

1.24

γ-Ge3N4

7.82

5.42

333

259

216

1.15

0.43

0.46

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