Analysis of Transition Mechanism of Cubic Boron Nitride Single Crystals under High Pressure-High Temperature with Valence Electron Structure Calculation

The possibilities of hexagonal boron nitride (hBN) and lithium boron nitride (Li ₃ BN ₂ ) transition into cubic boron nitride (cBN) under synthetic pressure 5.0 GPa and synthetic temperature 1700 K are analyzed with the use of the empirical electron theory of solids and molecules. The relative differences in electron density are calculated for dozens of bi-phase interfaces hBN/cBN, Li ₃ BN ₂ /cBN. These relative differences of hBN/cBN are in good agreement with the first order of approximation ( $<10\%$ ), while those of Li₃BN₂/cBN are much greater than 10%. This analysis suggests that Li ₃ BN ₂ is impossible to be intermediate phase but is a catalyst and cBN should be directly transformed by hBN. (paper)