Ab initio Structure Determination of Mg10Ir19B16

The ab initio structure determination of a novel unconventional noncentro-symmetric superconductor Mg10Ir19B16 (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 Mg10Ir19B16 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.