Pressure-induced polymorphism in Al3BC3: A first-principles study

Al3BC3, an isostructural phase to Mg3BN3, experienced no pressure-induced phase transformation that occurred in the latter material (J. Solid State Chem. 154 (2000) 254–256). The discrepancy is not clear yet. Using the first-principles density functional calculations, we predict that Al3BC3 undergoes a hexagonal-to-tetragonal structural transformation at 24 GPa. The predicted phase equilibrium pressure is much higher than the previously reported pressure range, i.e., 2.5–5.3 GPa, conducted on phase stability of Al3BC3. A homogeneous orthorhombic shear strain transformation path is proposed for the phase transformation. The transformation enthalpy barrier is estimated to yield a low value, i.e., 0.129 eV/atom, which ensures that the transformation can readily take place at the predicted pressure.

Relative enthalpy of tetragonal phase with respect to hexagonal phase at various pressures. The pressure-induced phase transformation occurs at about 2 and 24 GPa for Mg3BN3 and Al3BC3, respectively.Figure optionsDownload as PowerPoint slide