STRUCTURAL PHASE-TRANSITION OF NAH AND LIH UNDER HIGH-PRESSURE

The band structure is calculated self-consistently with the augmented spherical wave method for NaH and LiH up to nearly 100 GPa and 1.5 TPa, respectively. The phase transition of NaH (B1 to B2) is predicted with moderate accuracy at about 37 Gpa, the corresponding experimental pressure is 28-32 GPa at 300 K. The same transition is also predicted for LiH at about 0.66 TPa. This transition is expected because the compressibility of the B2 phase of LiH is, in contrast to the previous misleading interpretation, larger than that of the B1 phase under all pressures according to the present calculation. © 1990.