Ab initio investigation of structural (phase) changes in Lİ3N under high pressure

We study the pressure-induced phase transition of Lİ3N using the standard Kohn-Sham selfconsistent density functional method in the local density (LDA) approximations and provide a solid evidence about its high-pressure phase. As predicted in total energy calculations, Lİ3N undergoes a structural phase transformation from the hexagonal α-Lİ3N (P6/mmm) structure to a γ−Lİ3N (Fm3 ̅m) type structure with the application of hydrostatic pressure. We also characterize the transformation mechanism and propose two intermediate phases having C2/m and P-1 symmetries for the hexagonal α- Lİ3N to γ−Lİ3N type phase transformation of Lİ3N, which is different from the previously proposed mechanisms. We also study this phase transition using the total energy calculations and furthermore, the lattice constants, the bulk modulus, the pressure derivative of the bulk modulus, and equilibrium energies are obtained for both low and high pressure phases. Our predicted transition parameters and bulk properties are in good agreement with the earlier first principle simulations.