Thermophysical properties of the novel 2D materials graphene and silicene: insights from ab-initio calculations

Graphene, a 2D layer of sp(2) bonded carbon atoms in honeycomb arrangement, is a recently synthesized material, with exceptional mechanical, electronic, optical and thermal properties. Although theoretically studied since a long time, as it is the building block of graphite (a stacking of graphene layers), it was isolated as single or few layers only in 2004. Today graphene can be produced by several methods that depend on the quality and dimension of the material to be obtained. Applications of graphene are extensive in electronics, photonics, sensing and also in the field of energy generation and storage. Belonging to the same chemical group of carbon, also silicon could be in principle the ingredient of a 2D material similar to graphene, named silicene. It shares with graphene the peculiar optical and electronic properties and could provide a more easy compatibility with the existing silicon-based microelectronics technology. An extremely high thermal conductivity in the range 3000-5000 Wm(-1)K(-1) has been measured for graphene. Only few results exist instead on the thermal properties of silicene. In this work we report ab-initio calculations, based on density functional theory and density functional perturbation theory, that provide the ingredients for the determination of the thermal conductivity and specific heat of graphene, silicene and 2D silicon carbide. Ab-initio calculations solve Schrodinger equation without the need of empirical parameters, only knowing the chemical nature of the system constituents. The use of consolidated approximations employed in density functional theory allows the accurate prediction of several properties of materials.