Ab initio structure determination of Mg ₁₀ Ir ₁₉B ₁₆

The ab initio structure determination of a novel unconventional noncentro-symmetric superconductor Mg ₁₀Ir ₁₉B ₁₆ (T _c) 5 K) has been performed using a method that involves a combination of experimental data and calculations. Electron diffraction, X-ray powder diffraction, phase estimation routines, quantum mechanical calculations, high-resolution electron microscopy, and structural chemistry arguments are used. With the strengths of different methods used to eliminate the ambiguities encountered in others, the complete structure, including a very light B atom, has been determined with a high accuracy from impure polycrystalline powder samples, which suggests that the type of analysis described may be used to successfully address other similar intractable problems. The solved structure of Mg ₁₀Ir ₁₉B ₁₆ shows a complex nature that irregular coordination environments preclude a conversional description of compact packing of coordination polyhedra; however, it can be easier understood as ordered in an onion-skin-like series of nested polyhedra.