Lattice Anomaly of MgB(<i>h</i>-BN) under Anisotropic Compression

Abstract

We have examined the lattice and electronic properties of a hypothetical compound of magnesium boride (MgB) with a hexagonal boron-nitride (h-BN) type crystal structure using the first-principles molecular dynamics (FPMD) method. We found a lattice anomaly of MgB(h-BN) under uniaxial c-axis compression. Lattice constant a contracts 0.0017 and 0.0051 nm under c-axis compression with Pz = 50 and 100 GPa, respectively. This contraction implies that the Poisson ratio of MgB(h-BN) is negative.