Prediction of high thermoelectric potential in AMN₂ layered nitrides: Electronic structure, phonons, and anharmonic effects

Band structures, electronic transport coefficients, harmonic and anharmonic vibrational properties of novel layered nitrides have been studied to evaluate the potential for thermoelectric applications. Using first principles theoretical methods we predict that AMN₂ compounds with A = Ca, Sr, and Ba, and M = Ti, Zr, Hf may exhibit Seebeck coefficients in excess of 150 μV K^-1 and good electrical conductivities. The phonon dispersions indicate the presence of low lying optic modes that can lead to low thermal conductivity. The analysis of the mode resolved Grüneisen parameter points to large anharmonicity. In addition, we show that the A-site substitution controls the degeneracies at the top of the valence band and the anisotropy of the Seebeck tensors.