Investigation of the possible ternary nitrides in the system Li3N/Na3N

The energy landscapes of several compositions in the system LixNa6-xN2 (x = 0, 1,...,6) are explored. The best structure candidates are analyzed using quantum mechanical methods, and their enthalpies of formation are calculat ed. We find that among the ternary compounds the structure candidates for t he compositions x = 2 and 4 are the most stable ones, with the optimal stru ctures being ternary variations of the Li3N-type structure. However, at hig h pressures, phase transitions from Li3N- to Li3Bi-related structures shoul d occur for all compositions x, including Li3N itself. (C) 2000 Editions sc ientifiques et medicales Elsevier SAS. All rights reserved.