Novel nitrogen-rich lanthanum nitrides induced by the ligand effect under pressure

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 sp2 and sp3 hybridizations are formed in the N18 ring of LaN8. The ligand effect of La induces a novel 1-D chain-like N10 cage polymeric structure in LaN10 and stabilizes it under mild pressure (25 GPa). Moreover, the ligand effect of the introduced La atom on the N10 cage has been clarified by the analysis of the structural evolution behavior from I4̄3m-N10 to Imm2-LaN10. In addition, Imm2-LaN10 with excellent energy (4.56 kJ g-1) and explosive performance (Vd = 16.88 km s-1, Vp = 1887.53 kbar) is a good energetic material candidate.