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.
A new type corn-thresher was developed and tested for farms in Uzbekistan. Unlike to the existent threshers, this corn-thresher peels the husks of corn-cobs and threshes the kernel. At first parameters of the peeler-bars were researched theoretically, then three types of peeler bars were installed symmetrically on the surface of rotor of the corn-thresher and compared experimentally. The corn-thresher works qualitatively and it requires least metal and energy. The weight of corn-thresher is just 350 kg, consumes power amount is 5 KW and the work performance of the thresher in the pure time is 4600 kg/hour. During the theoretical research, the results were determined that, width of the peeler-bar should be bigger or equal than 4.8 cm (b
p
≥ 4.8 cm). Also, the distance between peeler-bar and concave should be equal to 38 mm (S
c
= 38). While we researched experimentally the types of peeler bars, three type of them, namely straight tooth, sloped tooth and fluted bar were tested. Their surface was compared between 36-44 mm distance of peeler-bar and concave. When the distance between sloped tooth peeler-bar and concave was 38-40 mm, we achieved to peeling well the husk of corn-cob, threshing better the kernels than other peelers, the most important was that any grain had not damaged when we analyzed results.
Silicon clusters with a diamond-like core and energetically competitive non-diamond clusters were comparatively studied using the nonconventional tight-binding molecular dynamics simulation method. Non-diamond clusters were constructed according to a quasi-onedimensional pentagon-based regular growth pattern. A non-trivial competition between surface and core reconstructions in the clusters, in order to reach energetically favorable atomic arrangements, was observed. This prevents unlimited growth via the one-dimensional pattern.Starting from Si 43 , there was substantial deviation from the stacked pentagon motif, and for Si 61 one end of these clusters became almost two-dimensional. The structure of clusters with a diamond-like core was subject to substantial reconstruction for the cluster sizes considered (≤ 71 atoms). By extrapolating the present results, a lower bound for the transition from non-diamond structure to diamond-like structure is estimated to be 115 atoms.
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