Ab initio density-functional study of the bridging addition of acrylonitrile on the Si(100) surface

Abstract

Acrylonitrile may react with the Si(100) surface in a number of ways. Fifteen different configurations have been identified. This study which complements an earlier study devoted to cycloadditions and bonds involving a single atom deals essentially with configurations involving cumulative double bonds. Factors affecting the relative stability of various mesomeric forms are shown to be the proximity to tetrahedral geometry and the compatibility of the dipole form with buckled structures. Tripods are shown to be a way to accommodate a priori unfavorable structures.

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…Thus, the buckling of a surface dimer on group IV (100)-2×1 surfaces, including all the electronic and geometrical factors that ultimately define the thermodynamics and kinetics of surface processes plays a deciding role in determining the selectivity of surface reactions. The DFT studies of Cobian et al [155,156] have specifically addressed the reactivity of silicon surface dimers in a context of their buckling and also found a variety of possible products. These authors also compared the theoretical description of the acrylonitrile chemistry with the previous studies of Choi and Gordon [153] and attempted to categorize the total of fifteen different surface configurations considered [156].…”

Thermodynamic factors limiting the preservation of aromaticity of adsorbed organic compounds on Si(100): Example of the pyridine

“…16 and 17) which is a DFT code which solves the Kohn-Sham equations 18 in a plane-waves basis set. Our technical choices are similar to several other lattice calculations devoted to organic molecules adsorbed on Si (100): 13,19,20 -A cutoff energy for the plane-waves basis equal to 450 eV has been used. -The system has been considered at equilibrium when the Hellmann-Feynman forces are smaller than 20 meV/Å.…”

“…Generally, structures with two, three, or four bonds are more stable: for instance, in acrylonitrile, 19,20 the dative bond is far from being the most stable one. Moreover this result is at variance with the lattice calculations of Kim et al, 13 and also with the cluster calculations of Tao et al, 8 who find the mode VIII to be energetically more favorable.…”

“…As discussed elsewhere, 20 the buckling of the Si dimers is a key factor for understanding the adsorption of polar molecules on the Si(100) surface. As stated by Cardillo and Becker 25 and by Chadi, 26 the building blocks of the various reconstructions are asymmetric dimers leading to c(4 × 2) and p(2 × 2) surfaces having similar energies and which are readily interconverted as the difference is simply in the phases of adjacent rows.…”

“…Following the method used by Cobian et al, 19,20 we have roughly analyzed the different contributions to the calculated heat release for both configurations. This analysis is presented in Fig.…”