Dispersion and density of states of phonons and electrons in an α-B12 crystal determined from first principles

• Published in: Optics and spectroscopy 2017-07, Vol.123 (1), p.70-75
• Main Authors: Mavrin, B. N., Reshetnyak, V. V.
• Format: Article
• Language: English
• Subjects: Atomic properties; Band spectra; Boron compounds; Charge transfer; Chemical bonds; Condensed-Matter Spectroscopy; Covalence; Crystal structure; Density of states; Dielectrics; Dispersion; Dynamic stability; Electron states; Electronic structure; Energy gap; Lasers; Optical Devices; Optics; Oscillator strengths; Phonons; Photonics; Physics; Physics and Astronomy; Plane waves; Splitting
• ISSN: 0030-400X; 1562-6911
• DOI: 10.1134/S0030400X17070165

Using the DFT method, we study the phonon properties of an α-B 12 rhombohedral crystal in the basis set of plane waves and its electronic structure in the localized basis set of Gaussians. It follows from the phonon dispersion that the crystal possesses a dynamical stability. The effective Born charges, the oscillator strengths, the transverse–longitudinal splitting, and the dielectric functions of dipole modes are calculated. We show that charge transfer from polar to equatorial atoms takes place in a В 12 icosahedron, while В–В bonds have predominantly a covalent character. In the density of states of acoustic modes, we reveal a structure that can manifest itself in the spectra of disordered boron compounds. From the dispersion of electronic bands, the occurrence of an indirect energy gap follows. The overlap of partial densities implies the hybridization of s and p electronic states in boron atoms.