Equation of state and compressibility of nickel semiboride

The compound Ni2B stabilizes in tetragonal structure at NTP with space group I4/mcm (No. 140), and lattice parameters; a= 0.499 nm and c=0.424 nm. The B–B bond distance is of about 0.212 nm and the B–B interaction is expected to be very small. High pressure x-ray diffraction study on this compound was carried out up to 28 GPa. It was seen that the compound remained stable throughout out this pressure range and the B–B distance decreased by about ~4%. Electronic structure calculations were carried out using the Full Potential Linear Augmented Plane Wave (FP-LAPW) method to understand its structural stability with respect to pressure. It is seen that the Fermi level lies on a plateau region with very low density of states, despite the compound being metallic in nature. Further, the computations at reduced volumes revealed that the density of states at EF almost remained constant with pressure, which has been attributed to its structural stability under pressure.