CuN10: A High-Energy-Density Pentazolates with Antiferromagnetic State

Abstract

The pentazolates have attracted intensive interest because of their intrinsic green and high-energy density features. However, the physical role of spin electrons in pentazolate compounds is still not yet revealed. In this work, we use a constrained first principle structure search method to investigate the energy landscape of copper(II) pentazolate. The most stable phase (P212121-CuN10) adopts a typical quare-layered configuration with the dsp2 hybridized Cu atoms. Interestingly, the four empty dsp2 hybridization orbitals fully coordinate with the lone pair electrons of pentazolate anions (cycle-N5ˉ), and the unpaired electron of Cu2+ cation occupy in 4p orbital, which induce a high peak (Van Hove singularity) at the Fermi level in density of states (DOS), will further cause instability. Instead, this high peak is split into two spin channels via the electron’s rearrangement, and the unpaired electrons transfer to dsp2 hybridization orbital and form an antiferromagnetic state. As a result, the spin electrons are demonstrated to effectively lower the DOS at the Fermi level and stabilize the structure by reducing the energy of 0.128 eV/formula. In addition, the energy density of P212121-CuN10 is 4.05 kJ/g, is 1.83 times than that of reported P212121-CuN5 (2.21 kJ/g), is a bit higher than that of known Pnma-CuN6 (3.84 kJ/g), indicating that P212121-CuN10 is a promising high-energy-density material.