Simulation of the Physical-Chemical and Electronic Properties of Lithium-Containing 4H–SiC and Binary Phases of the Si–C–Li System.

In the equilibrium model of the solid surface–adatom system, including a three-dimensional interfacial surface, changes in surface properties are considered, taking into account the chemical potential due to the action of surface tension. The relationship between chemical potential and electrochemical potential of the th component in an electrochemical cell is analyzed. Using the density functional theory (DFT), the adsorption, electronic, and thermodynamic properties of 2 × 2 × 1 and 3 × 3 × 1 supercells of crystalline compounds ( , where and are stoichiometric coefficients) of the boundary binary systems of the ternary phase diagram of are studied. The stability of phases and property calculations are carried out with the exchange-correlation functional within the framework of the generalized gradient approximation (GGA PBE). The parameters of the crystal structures of the compounds , the adsorption energy of the lithium adatom on a substrate, the electronic structure, and the thermodynamic properties of supercells are calculated. The thermodynamically stable configurations of the supercells having different locations are determined. The DFT GGA PBE calculations of the enthalpy of formation of compounds are carried out in the ternary system. Taking into account the changes in the Gibbs free energy in the solid-phase exchange reactions between binary compounds, equilibrium sections (connodes) in the concentration triangle of the phase diagram are established. An isothermal section of the phase diagram at 298 K is constructed. The patterns of diffusion processes that are related to the movement of particles on the surface layer of the sample are analyzed. The activation energy of lithium diffusion in is calculated from the Arrhenius type relation in two temperature ranges (769–973 K) and (1873–2673 K). [ABSTRACT FROM AUTHOR]