부산대학교 도서관

Using an evolutionary structure search algorithm lanthanum trifluoride (LaF3) has been examined under hydrostatic compression. The comparison of enthalpies of various candidate structures suggests that at ambient condition the tysonite structure (space group P-3c1) is the lowest enthalpy phase. Further it has been found that this structure transforms to a primitive orthorhombic structure (space group Pmmn) around ~19.5 GPa, which is in reasonable agreement with the experimental value of 16 GPa. Upon further compression the orthorhombic structure has been predicted to transform to another orthorhombic phase with space group symmetry Cmcm at ~150 GPa. The results of the static lattice calculations have been substantiated by testing the lattice dynamic stability of these phases in the regime of their structural stability. Additionally, various Raman active modes for both the P-3c1 and Pmmn structures have been calculated as a function of pressure. The theoretically derived Raman active modes calculated for both the phases at various pressures display a good agreement with the experimental data.