Synthesis of new La nitrides at high pressure and temperature

We have succeeded in synthesizing two new lanthanum nitrides in a supercritical nitrogen fluid at high pressure (about 30 GPa) and high temperature (about 2000 K), using a diamond anvil cell and a YAG laser heating system. These nitrides were found to be stable down to 5 GPa and ∼300 K in a nitrogen atmosphere. One of the new lanthanum nitrides is a cubic P lattice-type phase, which is a main phase synthesized nitride. The calculated lattice parameter is a=11.979Å at 5 GPa, 300 K. The other nitride is of a trigonal P lattice-type. The calculated lattice parameters are a=3.889Å and c=6.691Å at 5 GPa, 300 K. The most likely phase of the former new La nitride is Pa3̄La2N3+δ, the structure of which may be similar to the Ia3̄  Mn2O3-type (Ia80). The phase of the latter nitride is P3̄m1La2N3+δ, the structure of which is the same as the P3̄m1  La2O3-type (hP5).