A THEORETICAL APPROACH TO THE TIGHT-BINDING BAND-STRUCTURE OF LIQUID CARBON AND SILICON BEYOND LINEAR-APPROXIMATIONS

We present a study of the band structure of liquid Carbon and Silicon modelled in a Tight-Binding Hamiltonian approximation by means of an i ntegral equation approximation that includes non-linear corrections. T he theoretical predictions are contrasted with Tight Binding Molecular Dynamics simulations in which the energy bands are obtained by direct diagonalization of the Hamiltonian matrix. The results for Silicon an excellent, whereas in liquid Carbon only some of the qualitative feat ures of the band structure are captured by the non-linear corrections. We find that this can largely be understood as an effect of missing t hree-body correlation functions in the theoretical treatment of the en ergy bands. This is particularly crucial in the case of strongly direc tional and short range bonding, as it occurs in Carbon. (C) 1997 Ameri can Institute of Physics.