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V. Paul-Boncour, A. Lindbaum:
"Ab initio calculations on the formation of La_1-xNi₂";
Journal of Physics: Condensed Matter, 14 (2002), S. 3921 - 3929.

Abstract
First principle calculations have been performed to compare the stability of the stoechiometric LaNi2 compound, crystallizing in the cubic C15 structure, with that of the C15 superstructure compound La15Ni32 and the tetragonal La7Ni16 which both contain La vacancies. These results show that LaNi2 is not stable against decomposition in the two neighbouring phases La2Ni3 and LaNi3 of the La?Ni phase diagram, which means that LaNi2 cannot be formed. The formation of La vacancies allows the relaxation of the stresses caused by too short La?La distances and lowers the enthalpy of formation. The La7Ni16 phase is more stable than the cubic La15Ni32, but the enthalpy of formation of La15Ni32 lies only slightly above the critical value for stability. This small difference may explain that, with very pure lanthanum, the formation of a cubic La15Ni32 phase is not observed, but can be stabilized by the presence of impurities present in commercial La.