High-Pressure Polymeric Nitrogen Allotrope with the Black Phosphorus Structure

Abstract

Studies of polynitrogen phases are of great interest for fundamental science and for the design of novel high energy density materials. Laser heating of pure nitrogen at 140 GPa in a diamond anvil cell led to the synthesis of a polymeric nitrogen allotrope with the black phosphorus structure, bp-N. The structure was identified in situ using synchrotron single-crystal x-ray diffraction and further studied by Raman spectroscopy and density functional theory calculations. The discovery of bp-N brings nitrogen in line with heavier pnictogen elements, resolves incongruities regarding polymeric nitrogen phases and provides insights into polynitrogen arrangements at extreme densities.

Novel sulfur hydrides synthesized at extreme conditions

“…The samples were mainly characterized by single-crystal (sc-XRDp) and powder x-ray diffraction (XRDp) measurements. The subscript "p" in sc-XRDp emphasizes the very small, just a few microns size of the single crystals, for which a special approach to the high-pressure XRD data acquisition and analysis was recently developed in high-pressure crystallography [28], and its reliability demonstrated numerous times [35][36][37]. The x-ray diffraction data were acquired at the P02.2 and 13-IDD beamlines of PETRA III and the APS, respectively.…”

Understanding Periodic and Non-periodic Chemistry in Periodic Tables

“…The elementary substances of the group 15 elements P to Bi are solid polymers under ambient conditions, while until recently nitrogen was only known as a dimeric gas. Predicted polymeric 'black nitrogen' phases are now established at high pressures and temperatures (Cheng et al, 2020;Ji et al, 2020;Laniel et al, 2020). The lightest member of group 15 is not that different, if very different conditions are compared.…”

“…In fact the pre-halogen nonmetals share more distinctive properties than any other class of elements. While the noble gases, as elemental substances, can be characterized by their invisibility and torpidity, and the halogens by their variegated appearance and acridity, the non-metallic pre-halogen elements exhibit the following characteristics: (i) being sandwiched between the strongly electronegative halogen nonmetals and the 'weakly (non)metallic' metalloids, their physical and chemical character is overall 'moderately nonmetallic'; (ii) the elemental substances have a semi-metallic [graphitic carbon, black phosphorus (the most stable form under ambient conditions, now easily prepared by Tiouitchi et al, 2019), selenium] or colored (sulfur) or colorless (hydrogen, nitrogen, and oxygen) appearance and possess a brittle comportment if in solid phase (including N under high pressure: Cheng et al, 2020;Ji et al, 2020;Laniel et al, 2020); (iii) they show an overall tendency to form covalent compounds featuring localized and catenated bonds as chains, rings, and layers; (iv) in light of their relatively small atomic radii and sufficiently low ionization energy values, a capacity to form interstitial and refractory compounds (West, 1931;Goldschmidt, 1967;Glasson and Jayaweera, 1968;Wulfsberg, 2000); (v) prominent geological, biochemical (beneficial and toxic), organocatalytic, and energetic aspects (Akerfeldt and Fagerlind, 1967;Hutzinger, 1980;Dalko and Moisan, 2004;Nancharaiah and Lens, 2015;Vernon, 2020a).…”

Stabilization of Polynitrogen Anions in Tantalum–Nitrogen Compounds at High Pressure

“…Hitherto, only a few classes of compounds containing homonuclear polynitrogen species were stabilized at ambient conditions: azides (N 3 − ), [1] diazenides and pernitrides (N 2 x − ), [2, 3] pentazolates (N 5 − ), [4, 5] pentazenium (N 5+ ) salts, [6] and most recently Mg 2 N 4 containing cis ‐tetranitrogen (N 4 4− ) [7] . The application of pressure allows stabilizing polymeric nitrogen species either in nitrogen polymorphs like cg ‐N [8] and bp ‐N [9] or in compounds with metals (CsN 5 , [10] LiN 5 , [11] MgN 4 , [7] BeN 4 , [12] FeN 4 , [13, 14] etc.). Recent experimental and theoretical studies suggest that the choice of metal significantly affects the resulting connectivity of polymeric or oligomeric nitrogen frameworks in high‐pressure compounds and therefore it allows tuning the properties of the polynitrides [15–19] .…”