Cobalt–Nitrogen Compounds at High Pressure

Abstract

The high-pressure phase diagram of Co−N compounds is enriched by proposing five stable phases (Pnnm-Co 2 N, Pmn2 1 -Co 2 N, Pmna-CoN, Pnnm-CoN 2 , and P1̅ -CoN 4 ) and two metastable phases (P3̅ 1c-CoN 8 and P1̅ -CoN 10 ). A systematic study has been performed for revealing the novel polymeric nitrogen structure and the outstanding properties of predicted polynitrides, such as structural characterization, energy analysis, stability analysis, and electronic analysis. P3̅ 1c-CoN 8 with the novel layer-shaped Nstructure and P1̅ -CoN 10 with the novel band-shaped N-structure are first reported in this work. Moreover, P3̅ 1c-CoN 8 (6.14 kJ/g) and P1̅ -CoN 10 (5.18 kJ/g) with high energy density can be quenched down to ambient conditions. The proposed seven high-pressure phases are all metallic phases. A weak ionic bond interaction is observed between the Co and N atoms, while a strong N−N covalent bond interaction is observed in the Pnnm-CoN 2 , P1̅ -CoN 4 , P3̅ 1c-CoN 8 , and P1̅ -CoN 10 phases. The N atoms in the polynitrides hybridize in the sp 2 state, for which the hybrid orbitals are constructed by the σ bond or lone electronic pair. The charge transfer between the Co and N atoms plays an important role to the structural stability. Moreover, the vibrational analysis of P3̅ 1c-CoN 8 and P1̅ -CoN 10 phases is performed to guide the future experimental study.

The New High-Pressure Phases of Nitrogen-Rich Ag–N Compounds

“…At 150 GPa, the bond lengths of ten N–N bonds (N 1 -N 4 , N 4 -N 3 , N 3 -N 2 , N 2 -N 2 , N 2 -N 5 , N 5 -N 6 , N 6 -N 1 , N 6 -N 6 , N 4 -N 7 and N 7 -N 7 ) that are constructed by seven inequitable nitrogen atoms (N 1 ->N 7 ) are 1.286 Å, 1.315 Å, 1.270 Å, 1.286 Å, 1.274 Å, 1.282 Å, 1.254 Å, 1.318 Å, 1.277 Å and 1.261 Å, respectively. Up to now, the reported N-rings in the polynitrogen structures are the N 5 , N 6 , N 10 , N 12 , N 14 and N 18 rings [ 51 , 52 , 53 , 54 ]. As the construction unit of the layer structure, the novel N 7 rings and N 20 rings are firstly reported for this work.…”

“…The Immm-HfN 10 is discovered to be stable at moderate pressure above 23 GPa and can be preserved as a metastable phase at ambient pressure. The novel N 18 -ring, N 6 + N 10 -ring, N 10 -ring and N 18 -ring layered structures are found in P6/mcc-K 2 N 16 , C2/m-BaN 6 , P2 1 /c-BeN 4 and P-31c-CoN 8 compounds, respectively [ 31 , 51 , 52 , 53 ]. Moreover, the N 14 -ring band-shape structure is the first reported for P-1-CoN 10 [ 53 ].…”

“…The novel N 18 -ring, N 6 + N 10 -ring, N 10 -ring and N 18 -ring layered structures are found in P6/mcc-K 2 N 16 , C2/m-BaN 6 , P2 1 /c-BeN 4 and P-31c-CoN 8 compounds, respectively [ 31 , 51 , 52 , 53 ]. Moreover, the N 14 -ring band-shape structure is the first reported for P-1-CoN 10 [ 53 ]. The P-31c-CoN 8 (6.14 kJ/g) and P-1-CoN 10 (5.18 kJ/g) with high-energy density can be quenched down to ambient conditions.…”

Signal-specific reactivity of host-guest complexes controls supramolecular aggregate formation

“…Instead, we use 4-hydroxybutanohydrazide (Nu3), which is water soluble and has low affinity for cucurbiturils. [39] Using 1 H-NMR spectroscopy, we followed the conversion of 2 2+ (2 mM) upon reaction with 3 mM signal molecules (in 50 mM pH 7.4 sodium phosphate buffer). For Mesna, proline and ethanolamine, the reaction rates agrees very well with the reported nucleophilicity [40] as thiol> sec.…”

Novel high-pressure phases of nitrogen-rich Y–N compounds

“…The introduced foreign element with a distinct electronic valence state provides different bonding environments for the construction of novel polymeric structures. A great number of polynitrides (MN x ) with high nitrogen content have been reported in theory, such as MN 3 (M = Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Al, Sn, Sc, and Gd), [20][21][22][23][24][25][26][27][28][29][30][31][32] MN 4 (M = Be, Mg, Ca, Sr, Ba, Al, Ge, Sn, Fe, Co, Zn, Cd, Gd, and Ir), [25][26][27][28][29][30][32][33][34][35][36][37][38][39][40] MN 5 (M = Li, Na, K, Rb, Cs, Ca, Sr, Ba, Al, Ga, Sn, Sc, Cu, and Cd), 23,26,30,31,39,[41][42][43][44][45][46] MN 6 (M = Al, Ga, Sn, Ba, Fe, Zn, Cd, Gd, and W), 25,28,30,32,36,38,39,46,…”