First‐Principles Study of the Properties of Pmn21‐B_1−xAl_xAs

Abstract

A class of structures, Pmn21-B 1−x Al x As (x = 0, 0.25, 0.5, 0.75) is predicted and its mechanical, electronic and optical properties are calculated by first-principles calculations. The ground-state structural stability of Pmn21-B 1−x Al x As at 0 and 100 GPa pressure is confirmed by analyzing the obtained binding energies, enthalpy of formation, and phonon spectra. The calculated elastic constants, Poisson's ratio, shear modulus, and bulk modulus indicate that B 0.75 Al 0.25 As and BAs exhibit brittleness, and B 0.25 Al 0.75 As and B 0.5 Al 0.5 As exhibit ductility. The energy band structures of Pmn21-B 1−x Al x As (x = 0, 0.25, 0.5, 0.75, 1) calculated by the HSE06 mixing function are direct band gaps, and the band gaps are 1.833, 0.868, 1.498, 1.630 and 2.372 eV. The optical properties of Pmn21-B 1−x Al x As (x = 0, 0.25, 0.5, 0.75) are analyzed. For these four Pmn21-B 1−xx Al x As (x = 0, 0.25,0.5, 0.75), the static refractive indices n(0) are 2.53, 2.52, 2.52 and 3.11, and the peak reflection coefficients are 13.1, 12.5, 11.8 and 11.5 eV, respectively. The absorption spectrum is mainly in the range of 0 eV-18 eV, and the absorption spectrum maxima of Pmn21-B 1−x Al x As are located at 7.15, 6.7, 6.2 and 5.2 eV. The maximum real parts of conductivity of Pmn21-B 1−x Al x As (x = 0, 0.25, 0.5, 0.75) are located at 6.38, 6.1, 5.48 and 4.7 eV, respectively.