Buckling strain effects on the electron and the phonon spectra, the stability, thermal, and optical characteristics of an MgO nanosheet using PBE/GGA and HSE06

The stability, the electronic, the phonon , the thermal, and the optical properties of a buckled MgO monolayer are investigated using DFT with the PBE/GGA and the HSE06 functionals. Model calculations for a buckled MgO monolayer indicate a more interesting behavior than for its flat phase. The band gap decreases from 4.9 to 2.83 eV within the HSE06 approach due to increased electron density of states in the conduction band in the direction of the buckling. Both phonon dispersion and molecular dynamic calculations confirm the dynamic and the thermal stability of the buckled MgO monolayer. The heat capacity of a buckled monolayer is higher than for the flat one in a high temperature range due to a higher phonon density of states caused by the buckling effects. Furthermore, the buckled MgO monolayer has a higher static dielectric function leading to an increased ability to store electrical energy. The buckling creates wrinkles at the surface of the MgO monolayer that can localize collective electron oscillations , resulting in suppression of the plasmon frequency. The main intensity peak in the optical conductivity is red-shifted from the near-ultraviolet to the visible light region in the presence of buckling which may be beneficial for optoelectronic devices .