Observation of Atom Population, Electronic Structures and Optical Properties of β-Si_2Si_(1-x)Al_xN_4 (x = 0, 1/4, 1/2 and 3/4) Based on the First-Principles Calculations

摘要

The atom population, electronic structures, and optical properties of β-Si_2Si_(1-x)Al_xN_4 (x = 0, 1/4, 1/2 and 3/4) are analyzed using first-principles calculations with the generalized gradient approximation (GGA). Calculated formation energies are 3.1831, 5.9745, and 9.2447 eV, respectively, suggesting that the stability decreases gradually as the concentration of Al doping increases. The calculated band gaps are 4.213, 3.157, and 3.103, respectively, so the systems behave like semiconductors. The bond population value decreases with Al doping, indicating that a decline in bond strength of covalent bond occurs. Calculated static dielectric constants ε(0) obtained at the zero frequency limit of the real part of the dielectric function are 36.1, 40.7, and 35.4, respectively, implying their potential applications in electronic and optical components. The absorption band ranging from 5 to 16 eV changes a little narrow and splits into two peaks located at 9.78 and 11.23 eV for x = 3/4, accompanying a red-shift. In theoretical electron energy loss spectra, the values of host peaks located at 20 eV decrease gradually and shift to the low energy as the concentration of Al doping increases.