High-Order Elastic Constants and Anharmonic Properties of NaBH₄: First-Principles Calculations

We present theoretical studies for second- and third-order elastic constants in NaBH₄ based on ab initio calculations. Our calculated second−order elastic constants agree well with available experimental results. The anharmonic properties of NaBH₄ , such as pressure derivative of the second−order elastic constants and the Grüneisen constants for long-wavelength acoustic mode γ(q,j), are characterized using the third-order elastic constants.