Analytical Techniques & Modelling of the Lithium Hydride Ageing Reactions

Lithium hydride, the “lightest” inorganic salt possible, and the simplest neutral heteropolar diatomic molecule, has been the object of intense theoretical and spectroscopic study since the 1930s. Its unique nuclear chemistry and high hydrogen density allows it an unsurpassed place, in certain isotopic forms, in modern nuclear weapons. The basic chemistry is of great interest and the reaction with water has been extensively studied. However, much of the work reported to date has examined the reactions over relatively short timescales and been completely inconclusive in terms of the mechanisms/kinetics of lithium hydride chemistry and its long-term ageing. High vacuum mass spectroscopy leak detection studies of the very slow hydrogen evolution rates was/is the historical technique, but is not reported here. Research reported includes the use of modern analytical techniques such as solid state 6Li NMR, as well as an adapted thermal analysis technique specifically for atmospherically sensitive materials. Quantum mechanical modelling and molecular mechanical calculations of the basic hydride/water reactions are also reported. The research aims to expand our knowledge of the complex chemistry that occurs during the apparently simple long term hydrogen outgassing of bulk lithium hydride.