Structural Transformations in Na₃N under High Pressure

Addressing chemical diversity by employing the energy landscape concept

“…Sodium nitride Na 3 N. Another deceptively simple chemical system where a successful synthesis followed the prediction is Na 3 N. 8 In several studies Schö n et al, 2000Schö n et al, , 2001b, the enthalpy landscapes of all alkali nitrides M 3 N (M = Li, Na, K, Rb, Cs) were explored with simulated annealing and the threshold algorithm for a wide range of pressures. Furthermore, at intermediary pressures another modification exhibiting the YF 3 type was observed (Vajenine et al, 2008(Vajenine et al, , 2009) that resembles several structures found as local minima on the enthalpy landscapes of the alkali nitrides. Fig.…”

“…It appears to be only a matter of time until, for example, the predicted 5-5 structure type (Schö n & Jansen, 1995;Schö n, 2004;Č ančarević et al, 2008) that has already been realized as the aristotype of Li 4 SeO 5 (Haas & Jansen, 1999), and also been seen in thin films of ZnO (Claeyssens et al, 2005), will also have become accessible in the alkali halides or perhaps the earth alkali metal oxides. And, as mentioned above, a combination of the LT-ABD method and high-pressure syntheses has resulted in the successful synthesis of four previously predicted modifications of the elusive sodium nitride (Fischer & Jansen, 2002b;Vajenine et al, 2008Vajenine et al, , 2009.…”

“…Even more importantly, almost the full set of the most stable predicted, and published five years in advance, polymorphs of Na 3 N (see Fig. 1 and x5.1.2) have recently been realized (Vajenine et al, 2008(Vajenine et al, , 2009). This impressively documents the strength of our new rational way for solid-state synthesis, and this result has attracted a lot of interest, which in part arose because of generations of solid-state chemists having tried in vain to synthesize Na 3 N in the past.…”

“…5.1.2. Experimentally, the ReO 3 type (Fischer & Jansen, 2002b), the Li 3 N, the Li 3 P and the Li 3 Bi structure types (Vajenine et al, 2008(Vajenine et al, , 2009) have all been synthesized, the latter three using high-pressure experiments starting from the ReO 3 type. This resulted in a large number of structure candidates, including, for example, the Li 3 N, the Li 3 P, the Li 3 Bi, the AuCu 3 , the Al 3 Ti, the ReO 3 and the UO 3 structure types, plus many previously unknown structure types.…”

“…I-Na 3 N corresponds to a strongly distorted Li 3 Bi structure type with 12(+2)-fold coordination of the nitrogen atoms by sodium atoms. Experimentally, the ReO 3 type (Fischer & Jansen, 2002b), the Li 3 N, the Li 3 P and the Li 3 Bi structure types (Vajenine et al, 2008(Vajenine et al, , 2009) have all been synthesized, the latter three using high-pressure experiments starting from the ReO 3 type. Furthermore, at intermediary pressures another modification exhibiting the YF 3 type was observed (Vajenine et al, 2008(Vajenine et al, , 2009) that resembles several structures found as local minima on the enthalpy landscapes of the alkali nitrides.…”