  We investigate the electronic, the thermal, and the optical properties of
BN-codoped MgO monolayers taking into account the interaction effects between
the B and the N dopant atoms. The relatively wide indirect band gap of a pure
MgO nanosheet can be changed to a narrow direct band gap by tuning the B-N
attractive interaction. The band gap reduction does not only enhance the
optical properties, including the absorption spectra and the optical
conductivity, but also the most intense peak is shifted from the Deep-UV to the
visible light region. The red shifting of the absorption spectra and the
optical conductivity are caused by the attractive interaction. In addition,
both isotropic and anisotropic characteristics are seen in the optical
properties depending on the strength of the B-N attractive interaction. The
heat capacity is reduced for the BN-doped MgO monolayer, which can be referred
to changes in the bond dissociation energy. The bond dissociation energy
decreases as the difference in the electronegativities of the bonded atoms
decreases. The lower difference in the electronegativities leads to a weaker
endothermic process resulting in reduction of the heat capacity. An ab initio
molecular dynamics, AIMD, calculation is utilized to check the thermodynamic
stability of the pure and the BN-codoped MgO monolayers. We thus confirm that
the BN-codopant atoms can be used to gain control of the properties of MgO
monolayers for thermo- and opto-electronic devices.
