Predication of novel ordered phases in Cu-Be system at ambient pressure: Crystal structures, electronic properties, and alloying mechanism

The crystal and electronic structures determine a material's physical and chemical properties. Here, using particle swarm optimization method and first-principles calculations, we conducted a systematically investigation on the ordered CuxBey alloys. Two novel stable phase CuxBey (P4¯m2-CuBe3, and I4/mmm-Cu2Be) and five novel metastable CuxBey alloys (F4¯3m-CuBe5, P21/m-CuBe4, P4/mmm-Cu3Be, P4/mmm-Cu4Be, and P4/mmm-Cu5Be) are predicted for the first time. The primary alloying form of ordered CuxBey alloys is the substitution of certain Be atoms for some Cu atoms in the FCC-Cu according to structural study. Obvious valence electrons transfer from Be to Cu and the lattice interstice are observed, which leads to Cu exhibiting negative valence state in CuxBey and Be-rich CuxBey acting as zero-dimensional electrides. Furthermore, these Be-rich CuxBey have good structural stability due to the interaction between interstitial anionic electrons and Be atoms in the Be-tetrahedron. These findings help us in the design and application of CuxBey alloys and related materials.