Phonon spectrum and thermal properties of cubic Si3N4 from first-principles calculations

The phonon spectrum of cubic Si3N4 was calculated by first-principles techniques. The results permit an assessment of important mechanical and thermo-dynamical properties such as the bulk modulus, lattice specific heat, vibration energy, thermal expansion coefficient, and thermal Grüneisen parameter for this compound. The calculated phonon spectrum shows a gapless spectrum extending to a cutoff energy of ∼1030 cm−1. The calculated Raman- and infrared-active phonon frequencies are compared with measured data in the literature.