“…Second, the lithium halide seems to be af lux aiding the growth of single crystals without the need for additional NH 4 Cl (Figure 13). This might be correlated with the property of lithium halides of being asolvent for nitrides such as Li 3 N. [77,78] High-pressure metathesis has been shown to offer systematic access to rare-earth nitridophosphates by addition of starting materials such as Li 3 N, P 3 N 5 ,PON,P 2 O 5 ,and/or Li 2 O. Through the addition of Li 3 N, the degree of condensation can be lowered, resulting for example in two M 2 P 3 N 7 polymorphs with M = La, Ce,P r, Nd, Sm, Eu, Ho,Y bc onsisting of tetrahedra single layers with k = 3/7 [Eq.…”