Vibrational and Thermodynamical Properties of MgO Nanosheets of (111) and (100) Facets by Density Functional Theory
The interesting properties of 2D nanostructures provide a possibility for developing different applications for these materials. This study mainly focuses on investigating the phonon and thermodynamic properties of MgO (111) and MgO (100) nanosheets through first-principle calculations using density functional theory and density functional perturbation theory. The generalized gradient approximation in a plane wave basis was used for the exchange–correlation potential, and a quasi-harmonic approximation was employed to calculate the thermodynamic properties. The obtained phonon dispersion curves of MgO (111) and MgO (100) nanosheets indicated that the dynamical stability of both the studied samples of the nanosheet gradient of the acoustic branches was higher in MgO (100) than in MgO (111), which suggests a higher thermal conductivity of MgO (100). The total and partial phonon densities of states were specified and it was revealed that the acoustic phonons mainly result from the contribution of Mg, while the high frequency region of optical phonons derives from oxygen. The temperature variation of some thermodynamic properties, such as internal and Helmholtz free energies, entropy, specific heat capacity and Debye temperature (θD), were also investigated.