Stability of silicon carbide structures: From clusters to solid surfaces

We present a density-functional based non-orthogonal tight-binding (DF-TB) Hamiltonian in application to silicon carbide. The Kohn-Sham orbitals of the system are represented by a linear combination of atomic orbital (LCAO) equation with respect to a minimal basis of the localized valence electron orbitals of all atoms. Within a two-centre approach all Hamiltonian and overlap matrix elements are derived in a parameter-free way Yin the construction of pseudo-atomic orbitals and potentials by self-consistent single-atom calculations using the local-density approximation (LDA). This is in favour of a tabulation of the corresponding Slater-Koster integrals vs. distance. Making use of a non-self-consistent solution of the Kohn-Sham equations for the many-atom structure and an adjustment of the universal short-range repulsive two-particle potentials with respect, to self-consistent held (SCF)-LDA results in the method becoming sufficiently accurate to obtain the total energy of all-scale silicon carbide structures and this is transferable and efficient for predictive molecular-dynamics simulations. We present results for the energetic stability and properties of various microclusters and molecules including interactions with hydrogen. We give proof of the stability of the solid-state modifications and calculate the vibrational density of states for the most stable zinc blende structure. In addressing further applications to surface properties, we discuss the (1 x 1) reconstruction of the (110) SiC surface.