Ab initio exploration and prediction of AE-containing nitrido(litho/magneso)tetrelates (AE = Ca, Sr; Tt = Si, Ge) with [Si2N6]10− or [Ge2N6]10− units

Abstract

Recently, a number of different structurally related nitrides characterized by pairs of edge-sharing Si–N tetrahedra forming [Si₂N₆]¹⁰⁻ units have emerged via different synthesis methods. Concurrently, upon doping with rare earth elements (e.g. Eu²⁺ and Ce³⁺), numerous applications in the field of luminescent materials were revealed, ranging from the visible spectrum to the near IR. This compound class in turn emphasizes the extraordinary large tuning range with respect to relative composition by formal cation exchange. In this contribution, we study the dynamical stabilities of the existing Si-based nitridotetrelates and hypothetical Ge analogues promising for future synthesis efforts of luminescent materials by means of extensive phonon calculations. Further calculations of electronic and mechanical properties corroborate the fundamental suitability of the predicted compounds for the applications of potential luminescent materials with regard to band gap (E_g) and Debye temperature (Θ_D). Calculated enthalpies of the reaction provide further beneficial insights for future experimental attempts. Our study hence highlights a potential range of novel stable nitridogermanates with isotypic structures and suitable electronic properties for optoelectronic applications.