Crossings Of Potential Energy Curves Research Articles

Reaction of CH3CHO with Y+: A density functional theoretical study

The reaction mechanism of the Y+ cation with CH3CHO has been investigated with a DFT approach. All the stationary points are determined at the UB3LYP/ECP/6-311++G** level of the theory. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of a CH3CHO-metal complex followed by C-C, aldehyde C-H, methyl C-H and C-O activation. These reactions can lead to four different products (Y+CH4 + CO, Y+CO + CH4, Y+COCH2 + H2 and Y+O + C2H4). The minimum energy reaction path is found to involve the spin inversion in the different reaction steps, this potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

Theoretical survey of the reaction between osmium and acetaldehyde

The mechanism of the reaction of osmium atom with acetaldehyde has been investigated with a DFT approach. All the stationary points are determined at the UB3LYP/sdd/6-311++G** level of the theory. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of a CH3CHO-metal complex followed by C-C, aldehyde C-H, C-O, and methyl C-H activation. These reactions can lead to four different products (HOsCH3 + CO, OsCO + CH4, OsCOCH3 + H, and OsO + C2H4). The minimum energy reaction path is found to involve the spin inversion in the initial reaction step. This potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

Theoretical Investigation of the Reaction of Yttrium Cation with Acetone

Abstract The reaction mechanism of Y + with CH3COCH3 has been investigated with a DFT method. All the stationary points are determined at the UB3LYP/ECP/6-311++G** level of the theory. Both the ground and the excited state potential energy surfaces are investigated in detail. The present results show that the title reaction starts with the formation of an O-attached complex (IM0) followed by C–O, C–H and C–C activation. The minimum energy reaction path is found to involve the spin inversion in the initial reaction step. The potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

Theoretical survey of the potential energy surface of Zr + acetone reaction

The gas-phase reaction of zirconium atom with acetone is investigated using density functional theory. Geometries and energies of the reactants, intermediates, and products involved are calculated. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of an O-attached complex (IM0). All possible pathways starting with C O, C H, and C C activation are searched. These reactions can lead to four different products ( 3ZrO + C 3H 6, 2ZrCH 2COCH 3 + 2H, 3ZrCH 2 + CH 3CHO and 3ZrCOCH 2 + CH 4). The minimum energy reaction path is found to involve the spin inversion in the initial reaction step, and this potential energy curve-crossing dramatically affects reaction exothermic. As the triplet intermediates, transition states and products involved in the reaction lie below the ground reactants (Zr( 5F) + CH 3COCH 3) after IM1 formation, the reaction is expected to occur spontaneously over the triplet potential energy surface. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

DFT study of the reactions of Mo and Mo + with CO2 in gas phase

Density functional theory (DFT) calculations have been performed to explore the potential energy surfaces of C–O bond activation in CO2 molecule by gas-phase Mo + cation and Mo atom, in order to better understanding the mechanism of second-row metal reacting with CO2. The minimum energy reaction path is found to involve the spin inversion in the different reaction steps. This potential energy curve-crossing dramatically affects reaction exothermic. The present results show that the reaction mechanism is insertion-elimination mechanism along the C–O bond activation branch. All the theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction. For the reaction between Mo atom and CO2, it is found that the reaction system would likely to change its spin multiplicity twice in going from the entrance channel to the exit channel. Specifically, it can be described as 5Mo+CO2→5IM1→5TS12→5IM2→5TS23→CP4→3IM3→CP6→5MoO+CO.

Reaction of acetaldehyde with zirconium: A density functional theoretical study

The reaction mechanism of the Zr atom with CH 3CHO has been investigated with a DFT approach. All the stationary points are determined at the UB3LYP/ECP/6-311++G ** level of the theory. Both ground and excited state potential energy surfaces are investigated in detail. The present results show that the title reaction start with the formation of a η 2-CH 3CHO–metal complex followed by C C, aldehyde C H, methyl C H and C O activation. These reactions can lead to six different products (HZrCH 3 + CO, ZrCO + CH 4, ZrCH 2CO + H 2, ZrCOCH 3 + H, ZrCH 2CHO + H and ZrO + C 2H 4). The minimum energy reaction path is found to involve the spin inversion in the initial reaction step. This potential energy curve-crossing dramatically affects reaction exothermic. As the triplet intermediates, transition states and products involved in the reaction lie below the ground reactants (Zr( 5F) + CH 3CHO), the reaction is expected to occur spontaneously over the triplet potential energy surface. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

A density functional theory study on the reactions of Y atom and Y+ cation with carbonyl sulfide

The mechanism of the title reactions have been studied by using the DFT (B3LYP/ECP/6-311+G*) level of theory. Both ground and excited state potential energy surfaces are discussed. It is found the reaction mechanism is insertion mechanism both along the CS and CO bond activation branches, but the CS bond activation is much more favorable in energy than the CO bond activation. The reaction of Y atom with SCO was shown to occur preferentially on the ground state (doublet) PES throughout the reaction process, and the experimentally observed species, have been explained according to the mechanism revealed in this work. Different from that of Y + SCO system, the reaction between Y+ cation and SCO involves potential energy curve-crossing which dramatically affects reaction mechanism. Due to the intersystem crossing existing in the reaction process of Y+ with SCO, the intermediates SY+(η2CO) and OY+(η2CS) may not form. All our theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010

DFT Study of N2O Activation with La+, Hf+, Ta+ and W+ in the Gas Phase

AbstractThe spin‐forbidden reaction N2O(X1Δ)+M+→N2 (X1Σ+g)+MO+(M+=La+, Hf+, Ta+, W+) was discussed using density functional theory. The reaction mechanism between M+ transition metal ions and N2O is an insertion‐elimination one. All products are formed in exothermic processes. The potential energy curve crossings, which dramatically affect reaction mechanisms, were discussed in detail. In comparison with the previous work, an essential conclusion could be drawn that the reaction N2O(X1Δ)+CO(1Δ+)→N2(X1Σ+g)+CO2(1Σ+g) catalyzed by M+ was endothermic by 358.89 kJ·mol−1 which is in accord with the experiment finding.

CARBON DIOXIDE ACTIVATION BY Y ATOM AND Y+ CATION IN THE GAS PHASE: A DENSITY FUNCTIONAL THEORETICAL STUDY

ABSTRACT The potential energy surfaces for the Y+CO 2 and Y + +CO 2 reactions have been investigated by using the DFT (B3LYP/ECP/6−311+G*) level of theory. Both ground and excited state potential energy surfaces are discussed. The present results show that the reaction mechanism is an insertion mechanism along the C−O bond activation branch. The reaction of Y atom with CO 2 was shown to occur preferentially on the doublet PES throughout the reaction process. As for the reaction between Y + cation with CO 2 , it involves potential energy curve-crossing which dramatically affects reaction mechanism. Due to the intersystem crossing existing in the reaction process of Y + with CO 2 , the intermediate (OY(η 2 CO)) + may not form. This mechanism is different from that of Y + CO 2 system. All our theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction. Keywords: DFT theory, Potential energy surface, Intersystem, Yttrium

Theoretical investigation of the reactions of La atom and La+ cation with carbonyl sulfide

The potential energy surfaces for the La+SCO and La++ SCO reactions have been theoretically investigated by using the DFT (B3LYP/ECP/6-311+G(2d)) level of theory. Both ground and excited state potential energy surfaces (PES) are discussed. The present results show that the reaction mechanism is insertion mechanism both along the C-S and C-O bond activation branches, but the C-S bond activation is much more favorable in energy than the C-O bond activation. The reaction of La atom with SCO was shown to occur preferentially on the ground state (doublet) PES throughout the reaction process, and the experimentally observed species, have been explained according to the mechanisms revealed in this work. While for the reaction between La+ cation with SCO, it involves potential energy curve-crossing which dramatically affects reaction mechanism, and the crossing points (CPs) have been localized by the approach suggested by Yoshizawa et al. Due to the intersystem crossing existing in the reaction process of La+ with SCO, the products SLa+(η2CO) and OLa+(η2CS) may not form. This mechanism is different from that of La + SCO system. All our theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.

Theoretical study on the reactions of Zr+ and Zr with CO2 in gas phase

Density functional theory (DFT) calculations have been performed to explore the potential energy surfaces of C-O bond activation in CO2 molecule by gas-phase Zr+ cation and Zr atom, for better understanding the mechanism of second-row transition metal reacting with CO2. The minimum energy reaction path is found to involve the spin inversion in the different reaction steps. This potential energy curvecrossing dramatically affects reaction energetics. The present results show that the reaction mechanism is insertion-elimination mechanism along the C-O bond activation. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.

Carbon dioxide activation by La atom and La + cation in the gas phase: A density functional theoretical study

The potential energy surfaces for the La + CO 2 and La + + CO 2 reactions have been theoretically investigated by using the DFT (B3LYP/ECP/6–311+G(2d)) level of theory. To obtain an accurate evaluation of the activation barrier and reaction energy, the QCISD(T) single-point calculations using the B3LYP structures were performed. Both ground and excited state potential energy surfaces are discussed. These results show that the reaction mechanism is insertion mechanism along the C–O bond activation branch. The reaction of La atom with CO 2 was shown to occur preferentially on the ground state (doublet) PES throughout the reaction process, and the experimentally observed species, has been explained according to the mechanisms revealed in this work. As for the reaction between La + cation with CO 2, it involves potential energy curve-crossing which dramatically affects reaction mechanism, and the crossing points (CPs) have been localized by the approach suggested by Yoshizawa et al. Due to the intersystem crossing existing in the reaction process of La + with CO 2, the intermediate (OLa( η 2-CO)) + may not form. This mechanism is different from that of La + CO 2 system. All our theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.

Theoretical study of the reaction of Mo + with SCX (X=S, O) in gas phase

Density functional theory (DFT) calculations have been performed to explore the sextet, quartet, and doublet potential energy surfaces of C –X (X=S, O) bond activation in CS 2 and SCO molecules by gas-phase Mo + cation, in order to better understanding the reaction mechanism of second-row metal cations reacting with SCX (X=S, O). The minimum energy reaction path is found to involve the spin inversion in the different reaction steps. The crossing points (CPs) of the different potential energy surfaces (PESs) have been localized with the approach suggested by Yoshizawa et al. [K. Yoshizawa, Y. Shiota, T. Yamabe, J. Chem. Phys. 111 (1999) 538]. The potential energy curve-crossing dramatically affects reaction mechanism. The present results show that the reaction mechanism is insertion–elimination mechanism both along the C–S and C–O bond activation branches, but the C–S bond activation is much more favorable than the C–O bond activation in energy. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.

X-ray absorption and resonant Auger spectroscopy of O2 in the vicinity of the O 1s→σ* resonance: Experiment and theory

We report on an experimental and theoretical investigation of x-ray absorption and resonant Auger electron spectra of gas phase O(2) recorded in the vicinity of the O 1s-->sigma(*) excitation region. Our investigation shows that core excitation takes place in a region with multiple crossings of potential energy curves of the excited states. We find a complete breakdown of the diabatic picture for this part of the x-ray absorption spectrum, which allows us to assign an hitherto unexplained fine structure in this spectral region. The experimental Auger data reveal an extended vibrational progression, for the outermost singly ionized X (2)Pi(g) final state, which exhibits strong changes in spectral shape within a short range of photon energy detuning (0 eV>Omega>-0.7 eV). To explain the experimental resonant Auger electron spectra, we use a mixed adiabatic/diabatic picture selecting crossing points according to the strength of the electronic coupling. Reasonable agreement is found between experiment and theory even though the nonadiabatic couplings are neglected. The resonant Auger electron scattering, which is essentially due to decay from dissociative core-excited states, is accompanied by strong lifetime-vibrational and intermediate electronic state interferences as well as an interference with the direct photoionization channel. The overall agreement between the experimental Auger spectra and the calculated spectra supports the mixed diabatic/adiabatic picture.

Theoretical study of the reactivity of 4d transition metal ions with N 2O

The reactions of 4d transition metal ions (except Tc and Cd) with N 2O on two potential energy surfaces, producing the metal oxide ion and N 2, are studied by means of density functional theory. The results indicate that the lowest energy path corresponds to the η O 1 coordination of N 2O followed by the insertion of M + into the N–O bond. The reaction mechanism between 4d transition metal ions and N 2O is an insertion–elimination mechanism. All products are formed in exothermic processes. The potential energy curve crossings, which dramatically affect reaction mechanisms, are discussed in detail.

Theoretical study of the reaction of Sc + with SCO in gas phase

In order to elucidate the mechanism of reaction M + + SCO, both triplet and singlet potential energy surfaces (PESs) for the reaction of Sc + + SCO have been theoretically investigated using the DFT (B3LYP/6-311+G*) level of theory. The geometries for reactants, intermediates, transition states and products were completely optimized. All the transition states were verified by the vibrational analysis and the intrinsic reaction coordinate calculations. The involving potential energy curve-crossing dramatically affects reaction mechanism, reaction rate has been discussed, and the crossing points (CPs) have been localized by the approach suggested by Yoshizawa et al. The present results show that the reaction mechanism are insertion–elimination mechanism both along the C–S and C–O bond activation branches, but the C–S bond activation is much more favorable in energy than the C–O bond activation. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.

Theoretical study of the reaction of V + with SCO in gas phase

In order to elucidate the mechanism of reaction M + + SCO, the reaction of V + + SCO has been investigated using density functional theory (DFT) with the popular hybrid functional, B3LYP, in conjunction with 6-311+G∗ basis set both on the quintet and triplet potential energy surfaces (PESs). The crossing points (CPs) of the different potential energy surface (PESs) have been localized with the approach suggested by Yoshizawa et al. (K. Yoshizawa, Y. Shiota, T. Yamabe, J. Chem. Phys. 111 (1999) 538). The involving potential energy curve-crossing dramatically affects reaction mechanism. The present results show that the reaction mechanism is insertion–elimination mechanism both along the C–S and C–O bond activation branches, but the C–S bond activation is much more favorable than the C–O bond activation in energy. All theoretical results not only support the existing conclusions inferred from early experiment, but also complement the pathway and mechanism for this reaction.

Molecular rotation–vibration coupling by quantum wavepacket interference at potential energy curve crossings

Quantum wavepacket interference is shown to result in modulation of the ultrafast transient anisotropy of a diatomic molecule. The molecule is in a state comprising two bound electronic states at intermediate coupling strength and the anisotropy modulation enters via variations in the instantaneous contributions of the initial states to the total anisotropy. A necessary condition for the appearance of the modulation is that the involved rotational states possess different vibrational dynamics. The wavepacket interference mediates this coupling by imposing dynamical restrictions on the accessible vibrational phase space which depend on the rotational state.

Critical Bonding in Positive Homonuclear Diatomic Molecular Ions

Bonding in homonuclear diatoms with positive excess charge is considered. Focusing mainly onto two-electron systems, we analyze the explanation of barrier formation by avoided crossings of potential energy curves, and replace it by a description yielding a universal scenario for transitions from stable to metastable and unstable bonds in isoelectronic systems.

Model Calculations on Laser Induced Dissociation of Bromine with Control of Electronic Product Excitation

AbstractAfter a short survey of different methods to control electronic product excitations in laser‐induced unimolecular dissociations we develop an alternative strategy, adapted to interfering exit channels with potential energy curve crossings, and implement it for the bromine system. In a reference case with zero potential couplings optimal initial population of the competing dissociative states leads to complete product selectivity. In the real system, however, the electronically excited molecules pass the potential energy curve crossing of the B 3Πo + u and 1Π1u states on their way to dissociation, and Landau‐Zener‐type diabatic transitions establish the final product distribution. For this case we discuss the possibility to refine the electronic product distribution by a second, intense laser pulse applied after the curve crossing. Based on these results inversion of experimental product distribution data may be used to determine the curve crossing parameters, thus extending the short range information obtained from Raman scattering. Simulation of laser controlled dissociation is achieved by FFT (fast Fourier transform) propagation of representative wave packets.