Pressure-induced planar N6 rings in potassium azide

Abstract

The first-principles method and the evolutionary algorithm are used to identify stable high pressure phases of potassium azide (KN3). It has been verified that the stable phase with space group I4/mcm below 22 GPa, which is consistent with the experimental result, will transform into the C2/m phase with pressure increasing. These two phases are insulator with anions. A metallic phase with P6/mmm symmetry is preferred above 40 GPa, and the N atoms in this structure form six-membered rings which are important for understanding the pressure effect on anions and phase transitions of KN3. Above the studied pressure (100 GPa), a polymerization of N6 rings may be obtained as the result of the increasing compactness.

Effect of pressure on sodium azide studied by spectroscopic method

“…A series of pressure-induced phase transitions were observed in these substances and the interlayered shearing of unit cell and rotation of azide ions were revealed as the pressure below 30.0 GPa [12][13][14][15]17]. With increasing pressure, the azide ions were found to transform into chain like or ring structures then polymeric nitrogen nets [18][19][20][21]. Furthermore, the alkali metal cations were found to donate their electronic to change the electronic properties of nitrogen atom and compounds.…”

Structural phase transition and bonding properties of high-pressure polymeric CaN3

“…Recently, metal azides can be used as the starting materials to synthesize numerous types of potential high-energy-density materials because the synthesis pressure of metal azides is potentially lower than that of pure nitrogen gas. Over the years, various metal azides have been proposed in numerous experimental and theoretical studies, for example, LiN 3 , [13][14][15][16] LiN 5 , 13 NaN 3 , [17][18][19][20][21] KN 3 , 20,[22][23][24][25][26][27] CsN 3 , 23,28 and AlN 3 . 29 Moreover, N 2 H, 30,31 C-N system, 32,33 S-N system, 34 and the P-N system 35 are also studied as high-energy materials.…”

Can Cyclen Bind Alkali Metal Azides? A DFT Study as a Precursor to Synthesis

“…Metal complexes of macrocycles, such as crown ether, have the ability to activate anions by increasing their nucleophilicity . However, few studies have efficiently explored macrocycles as activating agents to trigger the formation of potentially high energy density polynitrogen compounds such as N 6 from alkali metal‐azide precursors. The synthesis and characterisation of the metal azide‐crown ether complexes of Li(12crown4), Na([15]crown‐5) and M([18]crown‐6), in which M=K, Rb and Cs, was perhaps the first effort in this direction .…”