Polymerization of nitrogen in two theoretically predicted high-energy compounds ScN₆ and ScN₇ under modest pressure

Abstract

Materials under high pressure usually exhibit unique chemical and physical properties. Polynitrogen compounds have received widespread attention as potential high energy density materials. This paper uses CALYPSO crystal structure prediction method to study the structures of ScN6 and ScN7 in 0-100 GPa. Theoretical calculations show that ScN6 is thermodynamically stable above 80 GPa, while ScN7 is thermodynamically stable from 30 GPa to 90 GPa. Furthermore, ScN7 is metastable under ambient conditions, demonstrating that it can be quenched to ambient conditions after high pressure synthesis. The P-1-ScN6 is a three-dimensional extended fold multi-nitrogen network, and the P-1-ScN7 contains a five-membered ring and a curved N4 molecular unit. Both P-1-ScN6 and P-1-ScN7 contain a lot of N-N single bonds and N=N double bonds. The energy densities of P-1-ScN6 and P-1-ScN7 are 3.97 kJ•g-1 and 3.12 kJ•g-1, respectively. The detonation velocity and detonation pressure of the P-1-ScN6 phase and P-1-ScN7 phase are also higher than that of TNT. Excellent energy storage properties and detonation performance show that they can be used as potential high-energy materials. These results opened up a new way for the synthesis of nitrogen-rich compounds.

Nitrogen-rich Ce–N compounds under high pressure

“…The detonation pressures of Pmn 2 1 -CeN 7 , Amm 2-CeN 9 , P 1̄-CeN 10 , and P 1̄-II-CeN 10 are 180.80, 171.79, 191.66, and 155.26 GPa, respectively, which are 5–10 times higher than those of TNT and 4–5 times higher than those of HMX. Moreover, these detonation pressure values are greater than those of some metal nitrides, such as BeN 4 , 18 ScN 6 , ScN 7 , 63 GdN 6 , 41 MN 10 (Be, Mg, Ca, Ba, and Y) 12,13 and MN 15 (M = Al, Ga, Sc, Y) 16 compounds. The detonation velocities of the four phases are between 15.34 and 17.03 km s −1 , which are about twice the detonation velocity of TNT.…”

One-Dimensional Non-coplanar Nitrogen Chains in Manganese Tetranitride under High Pressure

“…24 Because of the various valence electrons, transition metals (TM) as better electron donors had been extensively reported in first-principles calculations of polynitrides. 25−29 Theoretical calculations predicted the existence of different polynitrides MN x (M = transition metal, x = 4−10) featuring various polymeric nitrogen networks such as 1D infinity zigzag chains (ZnN 4 , 26,27 FeN 4 , 30,31 ), a 3D network (ScN 7 34 ), branched chains (TaN 5 36 ), and N 18 macrocycles (YN 6 37 ). On the one hand, these nitrides have a variety of properties because of the different nitrogen configurations.…”

“…Previous work has suggested that the introduction of metal elements will be an electron donor to stabilize the polymeric unit in polynitrides . Because of the various valence electrons, transition metals (TM) as better electron donors had been extensively reported in first-principles calculations of polynitrides. − Theoretical calculations predicted the existence of different polynitrides MN x (M = transition metal, x = 4–10) featuring various polymeric nitrogen networks such as 1D infinity zigzag chains (ZnN 4 , , FeN 4 , , and WN 8 ·N 2 ), triangular structures (IrN 4 ), N 5 rings (IrN 7 , ScN 6 , ZnN 10 ), armchair-like N 6 rings (WN 6 , , MoN 6 , ReN 6 ), a 3D network (ScN 7 ), branched chains (TaN 5 ), and N 18 macrocycles (YN 6 ). On the one hand, these nitrides have a variety of properties because of the different nitrogen configurations.…”