Interaction effects in a two-dimensional AlSi$_6$P nanosheet: A first-principles study on the electronic, mechanical, thermal, and optical properties

Physical quilities such as electronic, mechanical, thermal, and optical properties of Al and P codoped silicene forming AlSi$_6$P nanosheets are investigated by first-principle calculations within density functional theory. A particular attention of this study is paid to the interaction effect between the Al and P atoms in the buckled silicene structure. We infer that the interaction type is attractive and it leads to an asymmetry in the density of states opening up a band gap. In contrast to BN-codoped silicene, the buckling in the Al-P codoped silicene is not much influenced by the dopants as the bond lengths of Si-P and Al-P are very similar to the Si-Si bond lengths. On the other hand, the longer bond length of Si-Al decreases the stiffness and thus induces fractures at smaller values of applied strain in AlSi$_6$P. The elastic and nonelastic regions of the stress-strain curve of AlSi$_6$P depend on the placement of the Al and P atoms. The finite band gap caused by the Al-P dopant leads to enhancement of the Seebeck coefficient and the figure of merit, and induces a redshift of peaks in the dielectric response, and the optical conductivity. Finally, properties of the real and imaginary parts of the dielectric function, the excitation spectra, the refractive index, and the optical response of AlSi$_6$P are reported.