Hydrogen storage in a mixed system of lithium and sodium amide : A DFT modeling study

Abstract

Summary In the development of non-emissive hydrogen cars, an efficient and safe hydrogen storage method is needed. One possibility is reversible storage of hydrogen in solid materials. Throughout the last decade, intense research on complex metals hydrides has been made.

This thesis presents density functional calculations on the mixed compounds of lithium and sodium amides, Li8-xNax(NH2)8.

A mixture of LiNH2 and NaNH2 is found and confirmed to be stable: Li6Na2(NH2)8, as earlier reported.

Both the crystal and electronic state was calculated. The structure of Li6Na2(NH2)8 belongs to space group I-4. This is the same space which also belongs to LiNH2. Li6Na2(NH2)8 was found to have the unit cells parameters a = b = 5.135 Å and c =11.2(9) Å and angles α = β = γ = 90°.

This thesis is organized in six chapters. The introductory chapter gives a motivation for the study of hydrogen storage materials and a description of different storage materials, including metal hydrides. The following chapter describes the methodology that was used to perform the calculations in this work. The last three chapters present the results of the calculations on Li8-xNax(NH2)8, Chapter 3 presents the crystal structure, Chapter 4 presents the electronic structure, and Chapter 5 presents the stability of the structures. Chapter 6 contains the conclusion and draws the outlines of this thesis.