Elastic properties of MBH4 (M=Na, K, Rb, Cs)

The elastic properties of MBH4 (M=Na, K, Rb, Cs) are studied by first-principles calculations using a projected augmented plane-wave method and finite strain method. KBH4 is found to be the most isotropic material among MBH4, which can be attributed to the contribution of C44. The Debye temperatures are also calculated using theoretical elastic constants and the change along the series is explained.