First principle calculations of thermodynamic properties of pure graphene sheet and graphene sheets with Si,Ge,Fe,and Co impurities

The thermal properties of pure graphene and graphene-impurity (impurity = Fe, Co, Si, and Ge) sheets have been investigated at various pressures (0-7 GPa) and temperatures (0-900 K). Some basic thermodynamic quantities such as bulk modulus, coefficient of volume thermal expansion, heat capacities at constant pressure and constant volume of these sheets as a function of temperature and pressure are discussed. Furthermore, the effect of the impurity density and tensile strain on the thermodynamic properties of these sheets are investigated. All of these calculations are performed based on the density functional theory and full quasi harmonic approximation.