Lattice Anomaly of MgB (h-BN) and Related Compounds under Various Compression Conditions

Abstract

We study hexagonal materials of MgB (h-BN) and related compounds under various compression conditions. We found the anomalous behavior of lattice constants a (b) for MgB (h-BN) and HBC. Lattice constants a of MgB (h-BN) and HBC contract under c-axis compression. This means that the Poisson ratio is negative. The lattice contraction of a-axis is 0.0017 nm for MgB (h-BN) when P _z=50 GPa, 0.0002 nm for HBC when P _z=20 GPa. The contraction of HBC is quite small.

Keywords:

• First-principles
• Anisotropic compression
• Lattice anomaly
• Negative Poisson ratio
• Electronic structure

Acknowledgements

The numerical calculations were performed at NIMS (Namiki, AlphaServer GS140[HP]).