Theoretical analysis of x-ray absorption spectra of Ti compounds used as catalysts in lithium amide/imide reactions

We present a theoretical analysis and interpretation of the x-ray absorption near-edge structure of x-ray absorption spectroscopy (XAS) at the titanium K-edge of several Ti compounds for understanding catalysis mechanism in lithium amide LiNH(2) and imide Li(2)NH systems for hydrogen storage. Our theoretical approach is based on first-principles calculations using all-electron full-potential linear augmented plane-wave method. Chemical bonding and local geometry of catalytically-active Ti states in the hydrogen desorption reaction LiNH(2)+LiH -> Li(2)NH+H(2) are investigated. It is found that XAS spectra of some compounds consisting of elements Li, N, H, and Ti are quite similar to measured ones of catalytically-active Ti compounds. We conclude that Ti ions may occupy the Li sites in LiNH(2) during the reaction.