High-pressure formation of antimony nitrides: a first-principles study

Abstract

The structural phase transition, electronic properties, and bonding properties of antimony nitrides have been studied by using a first principles method.

High‐pressure and high‐temperature synthesis of crystalline Sb3N5

“…As expected from the involvement of the electron lone pair in the chemical bond formation, the SbÀ N distances in Sb 3 N 5 , ranging from 1.97 to 2.21 Å (Table SI-1), are consistent with the available experimental and calculated literature data at ambient pressure (section SI-3), with the single bond length values estimated from the sum of the calculated covalent radii of Sb and N (~2.1 Å) at ambient pressure [48] and with recently synthesized SbCN 3 at high pressure (2.0179 Å at 32.7 GPa, 2.022 Å at 32.8 GPa). [34] The SbÀ N bond lengths in Sb 3 N 5 are also in agreement with the SbÀ N bond lengths of the antimony nitride crystalline structures calculated by Lian et al [33] However, SbÀ N distances ranging between 2.35 and 2.56 Å at ambient pressure, comparable to our Sb02-N03 distances of 2.54 Å at 35 GPa, have been reported in the (PNP) 2 [Sb(pc 2À ) 2 ]Br•2 Et 2 O complex of Sb(V) (PNP = triphenylphosphine, pc = phthalocyaninate), where Sb exhibits square antiprismatic coordination by eight N atoms, four of which are located on one of two crown ether like chelating rings and four on the other. [49] Considering a cutoff SbÀ N single-bond length of 2.50 Å, well beyond the longest experimentally reported SbÀ N single bond length of 2.324(2) at ambient pressure ([Sb-(N 3 ) 5 ] 2À ) [45] in non-chelating ligands, and thus excluding the two Sb02-N03 distances of 2.54 Å (Table SI-1), the crystalline structure of Sb 3 N 5 can be described in terms of polyhedra as made of octahedral and trigonal prismatic SbN 6 units, respectively involving the Sb01 and Sb02 atoms, of NSb 4 distorted tetrahedra, respectively involving the N01 and N02 atoms, and of NSb 3 trigonal pyramids, involving the N03 atoms, which are illustrated in Figure 3 (panels A, B, C, G, H, I, L, M and N).…”

“…SbCN 3 , containing C, N and Sb, is made of guanidinate ([CN 3 ] 5À ) and Sb 5 + ions. [34] By this method, we report here the successful activation of a direct chemical reaction between Sb and N 2 in condensed phase under HP (32)(33)(34)(35) and HT (1600-2200 K) conditions generated by a laser heated DAC and the synthesis of a crystalline nitride of antimony with Sb 3 N 5 stoichiometry, whose structure was solved and refined using single crystal synchrotron XRD.…”

High‐pressure and high‐temperature synthesis of crystalline Sb3N5

“…Noticeably, SbN 4 , featuring higher N content, has been calculated to be a high-energy density material for the amount of released energy associated to its decomposition reaction into Sb and N 2 . [33] Sb and N 2 do not react spontaneously at ambient conditions and not even at high pressure along the room T isotherm. In this study we exploited pressure, statically generated by a membrane DAC, to increase the density and reduce the interatomic distances, and temperature, generated by laser heating, to overcome the thermodynamic and kinetic barriers and access new reactive paths.…”

“…In this respect, the ab initio structure search calculations performed by Lian et al [33] have provided further computational insight, predicting the existence of three dynamically stable crystalline polymorphs with different stoichiometry in the compositional space of the SbÀ N system at high pressure (SbN 2 , SbN 4 , Sb 2 N 3 ). Each of these structures, some of them containing N 2 molecules at low pressure, has been predicted to undergo a sequence of phase transitions with increasing pressure, essentially leading to a higher coordination number of Sb by N: Sb 2 N 3 (Cmcm, 100-120 GPa), SbN 2 (SbN 2 -I, C2/m, 12-23 GPa; SbN 2 -II, C2/m above 23 GPa), SbN 4 (SbN 4 -I, C2/m, 14-31 GPa; SbN 4 -II, P1 31-60 GPa; SbN 4 -III, P1 above 60 GPa).…”

“…SbCN 3 , containing C, N and Sb, is made of guanidinate ([CN 3 ] 5À ) and Sb 5 + ions. [34] By this method, we report here the successful activation of a direct chemical reaction between Sb and N 2 in condensed phase under HP (32)(33)(34)(35) and HT (1600-2200 K) conditions generated by a laser heated DAC and the synthesis of a crystalline nitride of antimony with Sb 3 N 5 stoichiometry, whose structure was solved and refined using single crystal synchrotron XRD.…”