Miao Sun

Substitution effect on the geometry and electronic structure of the ferrocene

The substitution effects on the geometry and the electronic structure of the ferrocene are systematically and comparatively studied using the density functional theory. It is found that NH2 and OH substituents exert different influence on the geometry from CH3, SiH3, PH2, and SH substituents. The topological analysis shows that all the CC bonds in a–g are typical opened‐shell interactions while the FeC bonds are typical closed‐shell interactions. NBO analysis indicates that the cooperated interaction of d → π* and feedback π → d + 4s enhances the Fe‐ligand interaction. The energy partitioning analysis demonstrates that the substituents with the second row elements lead to stronger iron‐ligand interactions than those with the third row elements. The molecular electrostatic potential predicts that the electrophiles are expected to attack preferably the N, O, P, or S atoms in FerNH2, FerOH, FerPH2, and FerSH, and attack the ring C atoms in FerSiH3 and FerCH3. In turn, the nucleophiles are supposed to interact predominantly by attacking the hydrogen atoms. The simulated theoretical excitation spectra show that the maximum absorption peaks are red‐shifted when the substituents going from second row elements to the third row elements.

Theoretical Study of Adsorption CO Molecule on Palladium-Doped Boron Nitride Nanotubes

By using the density functional theory (DFT), we have investigated CO molecules adsorbed on palladium atom doped (Pd-doped) (5, 5) and (6, 6) boron nitride nanotubes (BNNTs). In order to investigate the electronic and structural properties of all the research objects, we calculated the band gap (Eg), bind energy (Eb), and density of state (DOS). The results show that energy gaps of BNNTs reduced by doped impurity Pd atom, but there are no obvious changes with the tube diameter of Pd-BNNTs change. One impurity Pd atom substituting one B (PdB) or N atom (PdN) of pristine BNNTs can increase the reactivity with CO molecule. The energy gaps for CO molecule adsorption on the tube wall of Pd-BNNTs reduced. This indicates that Pd-doped BNNTs can be considered as nano gas sensitive material.

Theoretical study on the reaction of SiH(CH(3))(3) with SiH(3) radical.

The multiple‐channel reactions SiH3 + SiH(CH3)3 → products are investigated by direct dynamics method. The minimum energy path (MEP) is calculated at the MP2/6‐31+G(d,p) level, and energetic information is further refined by the MC‐QCISD (single‐point) method. The rate constants for individual reaction channels are calculated by the improved canonical variational transition state theory with small‐curvature tunneling correction over the temperature range of 200–2400 K. The theoretical three‐parameter expression k(T) = 2.44 × 10−23T3.94 exp(−4309.55/T) cm3/(molecule s) is given. Our calculations indicate that hydrogen abstraction channel R1 from SiH group is the major channel because of the smaller barrier height among five channels considered.

Theoretical studies on the reactions CH3SCH3 with OH, CF3, and CH3 radicals

The multiple‐channel reactions OH + CH3SCH3 → products, CF3 + CH3SCH3 → products, and CH3 + CH3SCH3 → products are investigated by direct dynamics method. The optimized geometries, frequencies, and minimum energy path are all obtained at the MP2/6‐31+G(d,p) level, and energetic information is further refined by the MC‐QCISD (single‐point) method. The rate constants for eight reaction channels are calculated by the improved canonical variational transition state theory with small‐curvature tunneling contribution over the temperature range 200–3000 K. The total rate constants are in good agreement with the available experimental data and the three‐parameter expressions k1 = 4.73 × 10−16T1.89 exp(−662.45/T), k2 = 1.02 × 10−32T6.04 exp(933.36/T), k3 = 3.98 × 10−35T6.60 exp(660.58/T) (in unit of cm3 molecule−1 s−1) over the temperature range of 200–3000 K are given. Our calculations indicate that hydrogen abstraction channels are the major channels and the others are minor channels over the whole temperature range.

Theoretical study and rate constants calculation for the reactions of SiH3 radical with SiH3CH3 and SiH2(CH3)2

The multiple‐channel reactions SiH3 + SiH3CH3 → products and SiH3 + SiH2(CH3)2 → products are investigated by direct dynamics method. The minimum energy path (MEP) is calculated at the MP2/6‐31+G(d,p) level, and energetic information is further refined by the MC‐QCISD method. The rate constants for individual reaction channels are calculated by the improved canonical variational transition state theory (ICVT) with small‐curvature tunneling (SCT) correction over the temperature range of 200–2400 K. The theoretical three‐parameter expression k1(T) = 2.39 × 10−23T4.01exp(−2768.72/T) and k2(T) = 9.67 × 10−27T4.92exp(−2165.15/T) (in unit of cm3 molecule−1 s−1) are given. Our calculations indicate that hydrogen abstraction channel from SiH group is the major channel because of the smaller barrier height among eight channels considered.

The Electronic Properties of Al-, P-Doped and Al, P Co-Doped Boron Nitride Nanotubes

The electronic properties of Al-, P-doped, and Al, P co-doped in a (6, 6) BN nanotubes were obtained using the first principle calculation based on the density functional theory. For the doped BNNTs, the structures are with ignorable deformation observed around the doping atoms. The analysis of the formation energies shows that aluminum replacement to be favorable, particularly in the case of the low concentration, and the stability of nanotubes has nothing to do with the doping position. The electronic band structure and DOS for the systems of Al-, and P-doped BNNTs all behave as impurity-doped widegap semiconductor. And as to the P-doped BNNTs, the conductivity becomes stronger with the higher concentration. Whereas, the results of the system of Al, P co-doped BNNTs illustrate that the electronic properties of nanotubes have nothing to do with the doping positions of impurity atoms.