N-rich La-N compounds have been studied by first-principles calculations in this work. We identified nine unknown polynitrides, which reveals that the miraculous ligand effect of La plays an important role in the electronic properties and hybridization of nitrogen atoms. Unique tri-coordination atoms with alternate sp 2 and sp 3 hybridizations are formed in the N 18 ring of LaN 8 . The ligand effect of La induces a novel 1-D chain-like N 10 cage polymeric structure in LaN 10 and stabilizes it under mild pressure (25 GPa). Moreover, the ligand effect of the introduced La atom on the N 10 cage has been clarified by the analysis of the structural evolution behavior from I 4̄3 m -N 10 to Imm 2-LaN 10 . In addition, Imm 2-LaN 10 with excellent energy (4.56 kJ g -1 ) and explosive performance ( V d = 16.88 km s -1 , V p = 1887.53 kbar) is a good energetic material candidate.