First-principles study of high pressure physical properties of bis(azidoformamidinium)5,5'-azotetrazolate(AFZT)
Bis(azidoformamidinium)5,5'-azotetrazolate(AFZT)of azotetrazole nonmetallic energetic salts has excellent detonation performance and has broad application prospects in the field of high explosives.In this pa-per,the crystal structure,electronic properties and hydrogen bond interactions of AFZT under 0~50 GPa pres-sure are calculated by the first-principle method based on density functional theory,and the variation laws of these properties under pressure are analyzed.The AFZT structure obtained by Generalized Gradient Approxima-tion-Perdew Burke Ernzerhof(GGA-PBE)combined method is in good agreement with experimental results,and phonon spectrum shows that it is stable at zero pressure.At zero pressure,AFZT is an indirect bandgap com-pound with a bandgap value of 1.962 eV,and there are eight hydrogen bond interactions between anions and cat-ions.Under pressure,the AFZT structure undergo structural transformation at 5 GPa,accompanied by the sud-den change of band gap value in the electronic structure.The band gap first decreases,then increases and then decreases,and the peak value of total density of states decreases with the increasing pressure.The N8-N9 and N9-N10 bonds on the cation are the most stable under pressure,and the hydrogen bond interactions of N-H…N type play the dominant role in AFZT structure.In addition,AFZT structure shows anisotropy when com-pressed,and the difficulty of compression along a crystal axis is related to the density of hydrogen bond interac-tion distribution in this direction.Its hydrogen bonds are mainly distributed along the xz plane and rarely in the y-axis direction,which makes AFZT most likely to be compressed along the y-axis direction.