In recent high resolution transmission electron microscopic studies we have found that high temperature vacuum annealing (1200–1800 K) of ultradispersed (2–5 nm) and micron size diamond produces fullerene-like graphitic species, namely, onion-like carbon and closed curved graphite structures (multilayer nanotubes and nanofolds), respectively. Here we undertake theoretical studies to help in the understanding of the experimental data for these systems. (1) Calculations of cluster models by a standard semiempirical method (MNDO a software package) are used to explain the preferential exfoliation of {111} planes over other low index diamond planes. (2) The same approach suggests the likelihood that the graphitization is initiated by a significant thermal displacement of a single carbon atom at temperatures close to the Debye temperature. (3) At the diamond–graphite interface we have observed the formation of two curved graphitic sheets from three diamond {111} planes. We suggest that the evolution of this interface proceeds by a “zipper”-like migration mechanism with the carbon atoms of the middle diamond layer being distributed equally between the two growing graphitic sheets. (4) The observed mosaic packaging of closed curved graphite structures during the diamond surface graphitization is suggested to be a self-assembling process. This process is explained in terms of the “stretching” of a bowed graphite hexagonal network. The stretch is due to the fact that, if relaxed, the network would be smaller than the initially transformed hexagonal diamond (111), and to the increased separation between the separated sheet and the surface. The initial phase of the process is studied quantitatively using a molecular mechanics simulation.

Adsorption species of ethyl benzoate (EB) on the (104) and (110) MgCl2 surfaces have been studied within DFT. As a result, monodentate and bidentate complexes of EB were obtained on both the MgCl2 surfaces. The bidentate structures on the (104) MgCl2 surface proved to be stabilized by the decreased distance between neighboring adsorption sites (surface Mg cations). The different affinity of EB for the five- and four-coordinated Mg cations predicted was suggested to be the cause of changing the equilibrium shape of MgCl2 crystals upon growing in the presence of EB: EB chemisorption seems to stabilize the (110) MgCl2 surface to a greater degree as compared to the (104) MgCl2 surface. The influence of EB coordination mode on active site stereoselectivity is discussed.

A systematic consideration of different Ti(IV) and Ti(III) species on the (104) and (110) MgCl 2 surfaces has been implemented within DFT using cyclic boundary conditions. Some new mononuclear and dinuclear surface complexes of Ti(IV) and Ti(III) were obtained due to implication of zip coordination mode. A possible spin state of dinuclear Ti(III) species was thoroughly studied: antiferromagnetic (ESR silent) state proved to be the most preferable in a number of cases. The zip antiferromagnetic Ti 2 Cl 6 complexes residing on the dominant (104) MgCl 2 surface make it possible to rationalize the fact that the most part of Ti(III) incorporated in activated MgCl 2 is ESR silent. Besides, these species produce aspecific active sites, thus explaining that aspecific centers significantly prevail over stereospecific one according to kinetic data on the simplest TiCl 4 /MgCl 2 þ AlR 3 system.

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A new semiempirical SCF MO procedure available for prediction of the transition-metal complexes' binding energy and molecular geometry is developed. The features of the method are (i) an explicit account of the orthogonality of the basis set; (ii) use of a new formula for the resonance integral; and (iii) an effective account of the Coulomb correlation of electrons in the calculation of the two-electron integrals based on approach of a model Coulomb hole function. The parameterization for H, C, N, 0, Co, and Ni atoms is presented. The results of NDDO/MC (NDDO for Metal Compounds) calculations of molecular geometries and binding energies for a number of organic compounds and more than 30 cobalt and nickel complexes are compared with the available experimental and ab initio data. The average absolute errors for the binding energies of organic molecules and metal complexes are 8.8 and 5.0 kcal/mol, respectively. 6

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