Crystallography of a new metastable phase in Zr–N alloy

Selected-area and convergent-beam electron diffraction were used to determine the lattice, point and space groups of a new metastable phase (designated the π phase) in the Zr–N system. The π phase has a body-centered tetragonal lattice with a ≃ 0.66 nm and a ca ratio of 0.81. The point-group symmetry of the phase is 4mmm and the space group is I4mmm.