The thermodynamic nucleation and the phase transition of cubic boron nitride $\left(c\text{−}\mathrm{B}\mathrm{N}\right)$ on nanoscale is performed with respect to the effect of nanosize-induced additional pressure on the Gibbs free energy of $c\text{−}\mathrm{B}\mathrm{N}$ critical nuclei and the phase transition probability from hexagonal boron nitride $\left(h\text{−}\mathrm{B}\mathrm{N}\right)$ to $c\text{−}\mathrm{B}\mathrm{N}$ in the $c\text{−}\mathrm{B}\mathrm{N}$ nanocrystals formation upon pulsed-laser ablation in liquid. The thermodynamic analysis showed that these $c\text{−}\mathrm{B}\mathrm{N}$ critical nuclei with smaller size of $20–30\mathrm{nm}$ and lower forming energy of ${10}^{-15}–{10}^{-14}\mathrm{J}$ could form in the pressure-temperature region of $4–5\mathrm{GPa}$ and $3000–3500\mathrm{K}$ created by pulsed-laser ablation in liquid, in the boron nitride equilibrium phase diagram. The phase transition probabilities of $h\text{−}\mathrm{B}\mathrm{N}$ to $c\text{−}\mathrm{B}\mathrm{N}$ are in the range of ${10}^{-5}–{10}^{-4}$ in the same pressure-temperature region. These theoretical results are well consistent with experimental data.

• Received 20 August 2004

DOI:https://doi.org/10.1103/PhysRevB.71.155422