Thermodynamic ground state of MgB6 predicted from first principles structure search methods

Exhaustive exploration of MgBn (n = 10–20) clusters and their anions

An unexpected tubular-shaped MgB₁₈ cluster is identified for the first time in alkaline-earth metal-doped boron clusters.

Novel magnesium borides and their superconductivity

With the motivation of searching for new superconductors in the Mg–B system, we performed ab initio evolutionary searches for all the stable compounds in this binary system in the pressure range of 0–200 GPa.

Coexistence of Superconductivity and Superhardness in Beryllium Hexaboride Driven by Inherent Multicenter Bonding

Unique multicenter bonding in boron-rich materials leads to the formation of complex structures and intriguing properties. Here global structural searches are performed to unearth the structure of beryllium hexaboride (BeB₆) synthesized decades ago. Three BeB₆ phases (α, β, and γ) were predicted to be stable at ambient and high pressures. The ground state at ambient pressure, α-BeB₆, consists of a strong and uniformly distributed covalent B-B network, which results in exceptional elastic properties and a hardness of 46 GPa comparable to γ-B. Even more surprisingly, α-BeB₆ retains credible electron phonon coupling in the boron sublattice, and is predicted to be superconducting at 9 K. Above 4 GPa, β-BeB₆ is stabilized with alternating boron slabs and triangular beryllium layers analogous to the structure of MgB₂. The β-BeB₆ is predicted to be superconducting at 24 K, similar to Nb₃(Al,Ge). The γ-BeB₆ is stable above 340 GPa. The understanding of intrinsic multicenter-bonding mechanism and related properties demonstrated in the very example of BeB₆ provides new insights for the design of tunable multifunctional materials.

A semiconductive superhard FeB₄ phase from first-principles calculations

An oP10-FeB4 phase [H. Gou, et al., Phys. Rev. Lett., 2013, 111, 157002] was recently synthesized based on previous theoretical predictions. In this study, a high-pressure phase of FeB4 (tP10-FeB4) was proposed through first-principles calculations. The tP10-FeB4 structure, which contains two formula units per unit cell, belongs to tetragonal symmetry with the space group P42/nmc. The boron atoms in tP10-FeB4 are present as tetrahedron configurations. Enthalpies as a function of pressure indicate that this new phase is probable to achieve through a phase transition from the oP10-FeB4 phase above ∼65.9 GPa. The softening of acoustic phonon at T points in the Brillouin zone may be the driving force behind the phase transition. Further analyses reveal that the tP10-FeB4 phase is a potential superhard semiconductor.