The principal differences between conventional tight-binding methods and a nonconventional tight-binding method proposed earlier by one of the authors ͓Z. M. Khakimov, Comput. Mater. Sci. 3, 95 ͑1994͔͒ are highlighted here. The latter has been optimized for simulation of the structure, cohesive energies, ionization potentials, and electronic affinities of silicon clusters. A single tight-binding approximation has been used to predict all of the above properties with accuracy comparable to state-of-the-art ab initio methods. This demonstrates the potential of tight-binding methods as a quantitative, predictive tool, provided they are based on an accurate total energy functional and exploit properly the individual properties of chemical elements, accounting for both intra-and interatomic charge redistributions.

Bare silicon clusters with non-diamond and diamond-core structures, as well as silicon-hydrogen clusters, were simulated using a recently developed non-conventional tight-binding molecular-dynamics method. In the range of cluster sizes considered (≤ 71 atoms), clusters with a diamond core were found to be energetically unfavorable compared to representative non-diamond clusters from a regular, one-dimensional growth pattern, proposed by the authors. It is shown that the method used here can reproduce the results of high-level ab initio methods including multi-level multistep methods such as G3/B3LYP.

The paper considers the computer model of silicon clusters doped with boron and phosphorus, and the effect of hydrogen on their structure and energy parameters. While calculating nanostructure formation, the model assumes hydrogenated Si29 clusters with substitution of a matrice atom with B and P impurities and insertion of one or some hydrogen atoms. Nanostructured defect complexes of SiP -H or Si-B-H are suggested to be formed under hudrogen insertion, with their stability depending on the hydrogen atom number and the dopant type. Computer modelling and optimization calculations were carried out in the frame of nonempyrical modelling methods for structure and properties of multiparticle systems-ORCA under the approximation of local electron state density.