We investigate the electronic structures, optical properties and perform a population analysis of the high-pressure phase of boron (γ-B28) by the norm-conserving pseudopotential density functional method. We employ the Perdew–Burke–Eruzerhof (PBE) form of the generalized gradient approximation (GGA) with plane-wave basis sets to expand the periodic electron density. The dielectric function and optical property constants including the reflectivity, the absorption coefficient, the refractive index, the electron energy-loss function and the optical conductivity are presented in an energy range from 0 to 22 eV. The calculated optical properties indicate that γ-B28γ-B28 could be an indirect gap optical material with unique properties. The population analysis suggests that the chemical bonding in γ-B28γ-B28 has predominantly covalent character and mixed covalent–ionic character.

Intermetallic compound superconductor MgB2 was synthesized from spherical magnesium powder and lower purity amorphous boron powder by microwave direct heating. Powder X-ray diffraction (XRD) analysis indicates that the phases of the synthesis sample are MgB2 (major phase) and a small amount of MgO. Scanning electron microscope (SEM) observation shows that the MgB2 grain size is homogeneous and the particle size is about several hundreds of nanometers. The onset superconducting transition temperature of the MgB2 sample measured by the temperature dependence of magnetization measurement is about 37.6 K. The critical current density Jc calculated according to the Bean model are about 2.0 × 105 A/cm2 at 20 K in self-field and 1.0 × 105 A/cm2 at 20 K in 1 T applied field.