An ab initio investigation of the electronic structure of lithium azide (LiN3), sodium azide (NaN3), and lead azide [Pb(N3)2

Abstract

Solid energetic substances have long played an important technological role as explosives, as well as for fuels. In this article, the authors concentrate on a type of explosive considered a primary explosive, lead azide, and its related compounds, lithium azide and sodium azide. Recent interest in more fundamental questions relating to the basic properties of these systems as materials, coupled with a desire to probe fundamental questions relating to the initiation and sustaining of the chemical reactions leading to combustion/detonation, is generating significant interest in the basic solid-state properties of such energetic systems. In particular, recent analysis of detonation by Gilman emphasizes the need to include excitation of the electronic system in obtaining an understanding. In this article, the band structures of the three solid metal azides are studied. This is done for both the normal lattice geometry and also in isotropically compressed geometries. These studies found that the alkali azide band gaps are far wider than is the lead azide gap and the lead azide gap is far more sensitive to narrowing with lattice compression than are the gaps for the alkali azides. In fact, the gap for sodium azide is found to widen with compression rather than narrow. The authors found that there is much seen in the band structures of these azides to lend some support to the Gilman model and also to demonstrate the importance of solid-state effects on the electronic structure and possible behavior of such energetic systems. © 1997 John Wiley & Sons, Inc.