531 / 2019-03-19 22:15:48

A Prediction of Energetic Materials: Alkaline Earth Metal Pentazolate

pentazolate,high-energy density material,high-pressure,crystal structure prediction

全体主题 > High Pressure Physics and Materials Science

Singly or doubly bonded polynitrogen as a high-energy density material (HEDM) can decompose to dinitrogen (N2) with an extremely large energy release, however, the difficulty of preserving polynitrogen thwarts attempts to discover extended nitrogen structures. Mixing nitrogen with electropositive elements to obtain viable solid-state compounds represents one approach to overcome thermodynamic/kinetic instability barrier. In this work, motivated by the novel experimental and theoretical discovery, we explored the MN10 stoichiometry, where M represents alkaline earth elements, e.g., Be, Mg, Ca, Sr and Ba at ambient pressure and 50 GPa using molecular crystal structure prediction based on evolutionary algorithms and density functional theory. Several new high-nitrogen content materials, containing pentazolate units, have been uncovered. Most of the compounds, featuring pentazolate anions in the crystalline state, are thermodynamically stable at high pressures. While, the zero pressure phases are metastable at ambient conditions. For this series, we find that the N5− ion can coordinate to the metal cation which forms from 1 to 3-dimensional network through either ionic or covalent interactions. Moreover, we will analyze the cation size effect on the structural, energetic and electronic properties which indicate pentazole–metal complexes might potentially serve as a new class of high-energy density materials.