Co-reporter:Chunfang Zhang;Yujun Zheng;Jianwei Cao
RSC Advances (2011-Present) 2017 vol. 7(Issue 55) pp:34348-34355
Publication Date(Web):2017/07/07
DOI:10.1039/C7RA03966B
The isotopic product CD/CH branching ratios, thermal rate coefficients, as well as other dynamical quantities of the C(1D) + HD → CD(H) + H(D) reaction are investigated by detailed quasiclassical trajectory calculations on the highly accurate singlet ground-state (ã1A′) and the first excited-state (1A′′) global ab initio potential energy surfaces (PESs) recently constructed by us. The calculated CD/CH branching ratios are in reasonable agreement with experiment. The thermal rate coefficients in the temperature range of 200–1500 K are calculated, and the obtained values at room temperature are in very good agreement with available experimental data. The distinct topographical features between the present and previous PESs, which influence the CD/CH branching ratio, are also discussed. In addition, the effect of the 1A′′ PES is investigated, and the results show that the contribution from the 1A′′ PES to the total reactivity is rather noticeable.
Co-reporter:Yinghui Ren
The Journal of Physical Chemistry Letters 2015 Volume 6(Issue 10) pp:1824-1829
Publication Date(Web):April 29, 2015
DOI:10.1021/acs.jpclett.5b00672
We present the first accurate quantum dynamics calculations of mode-specific tunneling splittings in a sequential double-hydrogen transfer process. This is achieved in the vinylidene–acetylene system, the simplest molecular system of this kind, and by large-scale parallel computations with an efficient theoretical scheme developed by us. In our scheme, basis functions are customized for the hydrogen transfer process; a 4-dimensional basis contraction strategy is combined with the preconditioned inexact spectral transform method; efficient parallel implementation is achieved. Mode-specific permutation tunneling splittings of vinylidene states are reported and tremendous mode-specific promotion effects are revealed; in particular, the CH2 rock mode enhances the ground-state splitting by a factor of 103. We find that the ground-state vinylidene has a reversible-isomerization time of 622 ps, much longer than all previous estimates. Our calculations also shed light on the importance of the deep intermediate well and vibrational excitation in the double-hydrogen transfer processes.
Co-reporter:Ying Wu, Chunfang Zhang, Jianwei Cao, and Wensheng Bian
The Journal of Physical Chemistry A 2014 Volume 118(Issue 24) pp:4235-4242
Publication Date(Web):May 30, 2014
DOI:10.1021/jp504411j
Quasiclassical trajectory (QCT) calculations have been performed on a new global ab initio potential energy surface (PES) for the singlet ground state (11A′) of the CH2 reactive system. Our new PES can give a very good description of the well and asymptote regions, and particularly regions around conical intersections (CIs) and of van der Waals (vdW) interactions. The integral cross sections, differential cross sections, and product rovibrational state distributions for the C(1D) + H2 → CH + H reaction have been investigated in a wide range of collision energies. The present integral cross sections are much larger than the previous QCT results at low collision energies, which can be attributed to the differences of the PESs in the regions around the CIs and vdW complexes. The thermal rate coefficients in the temperature range 200–1500 K have also been calculated and very good agreement with experiment is obtained.
Co-reporter:Lu Pan; Wensheng Bian
ChemPhysChem 2013 Volume 14( Issue 6) pp:1264-1271
Publication Date(Web):
DOI:10.1002/cphc.201200952
Abstract
Polybrominated diphenyl ethers (PBDEs) have received special environmental concern due to their potential toxicity to humans and wildlife worldwide, however, it is difficult to reveal their dominant photochemical degradation pathways by experiment. We explored the reaction mechanisms of photochemical degradation–debromination of three nona-BDEs in methanol using theoretical calculations, in which time-dependent density functional theory (TDDFT) combined with the polarizable continuum (PCM) model is applied. The selectivity of debromination was studied, and the major octa-BDE products photochemically debrominated from nona-BDEs were identified. We find that the debromination reaction results from the electronic transitions from π to σ* orbitals when nona-BDEs are exposed to UV-light in the sunlight region, at which point the two low-lying excited states for each nona-BDE are πσ*(5Br) and πσ*(4Br), which correlate to the σ* orbitals located on the penta-Br and tetra-Br substituted phenyls, respectively. Our calculations indicate that each nona-BDE may degrade to form three kinds of octa-BDE products via the πσ*(5Br) state, whereas only one kind of octa-BDEs can be formed via the πσ*(4Br) state. Our calculations can interpret the recent experiments successfully.
Co-reporter:Lu Pan, Wensheng Bian, and Jiaxu Zhang
The Journal of Physical Chemistry A 2013 Volume 117(Issue 25) pp:5291-5298
Publication Date(Web):May 31, 2013
DOI:10.1021/jp403958g
Polybrominated diphenyl ethers (PBDEs) have received special environmental concern because of their potential toxicity to humans and wildlife worldwide. However, their photochemical degradation mechanisms remain largely unknown. Herein, a PCM/TD-DFT scheme (time-dependent density functional theory combined with the polarizable continuum model) augmented with explicit solute–solvent interactions is used to explore the promotive effects of the toluene solvent on the photochemical degradation debromination of deca-BDE (BDE209). The face-to-face π–π interactions between penta-bromine-substituted phenyl and toluene are investigated. The calculations indicate that the face-to-face π–π interaction plays an important role in the low-lying π→σ* transitions of BDE209–toluene π-stacking complex at around 300 nm in the sunlight region, which leads to notable changes for the πσ* excited states and which promotes the breaking of the C–Br bonds. The photodegradation reaction via an intermolecular charge-transfer excited state formed by the electronic transition from a π orbital of toluene to a σ* orbital of BDE209 is found to be a dominant mechanism. Our calculation results reveal the mechanism of how the participation of an explicit toluene solvent molecule catalyzes the photodegradation of BDE209 and explain the experimental results successfully. The present study may provide helpful information for the removal of PBDE contamination.
Co-reporter:Zhijun Zhang, Bin Li, Zhitao Shen, Yinghui Ren, Wensheng Bian
Chemical Physics 2012 400() pp: 1-7
Publication Date(Web):25 May 2012
DOI:10.1016/j.chemphys.2012.01.010
We present full-dimensional quantum mechanical calculations of the vibrational states of acetylene. The calculation scheme is a combination of several methods. The molecular Hamiltonian is represented in CH–CH diatom–diatom Jacobi coordinates. Phase space optimized discrete variable representation is used to construct effective one-dimensional basis functions for radial coordinates, and a basis contraction strategy is applied to angular coordinates. Parity and diatom–diatom permutation symmetry are exploited. The final Hamiltonian matrix is sparse, and an iterative technique combined with an efficient preconditioner is employed to calculate the eigenvalues within desired spectral windows. It is shown that our computation is efficient and accurate, and nearly ideal scaling with respect to increasing energy is achieved.Graphical abstractHighlights► Full-dimensional calculations of vibrational states of acetylene are performed. ► The calculation scheme is accurate and efficient. ► Nearly ideal scaling with respect to increasing energy is achieved. ► The normal-to-local mode transition observed experimentally is confirmed.
Co-reporter:Yinghui Ren, Bin Li and Wensheng Bian
Physical Chemistry Chemical Physics 2011 vol. 13(Issue 6) pp:2052-2061
Publication Date(Web):24 Dec 2010
DOI:10.1039/C0CP01186J
Full-dimensional quantum dynamics calculations of vinylidene–acetylene isomerization are performed and the state-specific resonance decay lifetimes of vinylidene(-d2) are computed. The theoretical scheme is a combination of several methods: normal coordinates are chosen to describe the nuclear motion of vinylidene, with both the parity and permutation symmetry exploited; phase space optimization in combination with physical considerations is used to generate an efficient discrete variable representation; the reaction coordinate is defined by us according to the three most relevant normal coordinates, along which a kind of optimal complex absorbing potential is imposed; the preconditioned inexact spectral transform method combined with an efficient preconditioner is employed to extract the energies and lifetimes of vinylidene. The overall computation is efficient. The computed energy levels generally agree with experiment well, and several state-specific lifetimes are reported for the first time.
Co-reporter:Bin Li;Yinghui Ren; Wensheng Bian
ChemPhysChem 2011 Volume 12( Issue 13) pp:2419-2422
Publication Date(Web):
DOI:10.1002/cphc.201100144
Co-reporter:Kun Liu, Le Yu and Wensheng Bian
The Journal of Physical Chemistry A 2009 Volume 113(Issue 9) pp:1678-1685
Publication Date(Web):February 9, 2009
DOI:10.1021/jp809618y
The potential energy curves of the 23 Ω states generated from the 12 valence Λ−S states of silicon monochloride cation are calculated for the first time using the internally contracted multireference configuration interaction method with the Davidson correction and entirely uncontracted cc-pV5Z basis set. Spin−orbit coupling is taken into account by the state interaction approach with the full Breit−Pauli Hamiltonian. Very good agreement is achieved between our computed spectroscopic properties and the available experimental data. In particular, the adiabatic excitation energies of the a3Π0+ and a3Π1 states computed by us are 31 708 and 31 830 cm−1, respectively, in excellent agreement with the respective experimental values of 31 721 ± 2 and 31 836 ± 3 cm−1. The curve crossings and the predissociation mechanism are investigated. The transition dipole moments are analyzed and the transition properties of the a3Π0+−X1Σ0++ and a3Π1−X1Σ0++ transitions are predicted, including the Franck−Condon factors and the radiative lifetimes.
Co-reporter:Jianwei Cao;Kun Liu;Zhijun Zhang;Chunfang Zhang;Manhui Wang
PNAS 2009 Volume 106 (Issue 32 ) pp:13180-13185
Publication Date(Web):2009-08-11
DOI:10.1073/pnas.0903934106
This work elucidates new atomic-level mechanisms that may be common in a range of chemical reactions, and our findings are
important for the understanding of the nature of polyatomic abstraction and exchange reactions. A global 12-dimensional ab
initio potential energy surface (PES), which describes both H+SiH4 abstraction and exchange reactions is constructed, based on the modified Shepard interpolation method and UCCSD(T)/cc-pVQZ
energy calculations at 4,015 geometries. This PES has a classical barrier height of 5.35 kcal/mol for abstraction (our best
estimate is 5.35 ± 0.15 kcal/mol from extensive ab initio calculations), and an exothermicity of −13.12 kcal/mol, in excellent
agreement with experiment. Quasiclassical trajectory calculations on this new PES reveal interesting features of detailed
dynamical quantities and underlying new mechanisms. Our calculated product angular distributions for exchange are in the forward
hemisphere with a tail sideways, and are attributed to the combination of three mechanisms: inversion, torsion-tilt, and side-inversion.
With increase of collision energy our calculated angular distributions for abstraction first peak at backward scattering and
then shift toward smaller scattering angles, which is explained by a competition between rebound and stripping mechanisms;
here stripping is seen at much lower energies, but is conceptually similar to what was observed in the reaction of H+CD4 by Zare and coworkers [Camden JP, et al. (2005) J Am Chem Soc 127:11898–11899]. Each of these atomic-level mechanisms is confirmed by direct examination of trajectories, and two of them
(torsion-tilt and side-inversion) are proposed and designated in this work.
Co-reporter:Wenwei Zhao, Wensheng Bian
Journal of Molecular Structure: THEOCHEM 2008 Volume 859(1–3) pp:73-78
Publication Date(Web):30 June 2008
DOI:10.1016/j.theochem.2008.03.004
A theoretical study on various properties of the ground and first excited states of two 7-aminocoumarin dyes with heterocyclic substituents at the 3-position is presented. The ground-state and excited-state geometries were optimized at the Hartree–Fork and configuration interaction singles levels of theory, respectively. The geometric relaxation between the first excited state and the ground state was examined and explained in terms of the nodal patterns of the highest occupied and lowest unoccupied molecular orbitals. The most striking geometrical relaxation is the twisting motion between the parent coumarin and heterocyclic substituent at the 3-position. The absorption and emission wavelengths were calculated using the time-dependent density functional theory, and the solvent effect on geometries and spectra has been taken into account using the polarized continuum model. Our calculated results are in good agreement with the experimental measurements, and the influences of solvents and heterocyclic substituents on spectra are also discussed.
Co-reporter:Wenwei Zhao;Lu Pan ;Jianping Wang
ChemPhysChem 2008 Volume 9( Issue 11) pp:1593-1602
Publication Date(Web):
DOI:10.1002/cphc.200800131
Abstract
The characteristics of the electronic transition energy of Coumarin 120 (C120) and its H-bonded complexes in various solvents have been examined by time-dependent density functional theory (TDDFT) in combination with a polarizable continuum solvent model (PCM). Molecular structures of C120 and its H-bonded complexes are optimized with the B3LYP method in PCM solution, and the dihedral angle H14N13C7H15 is dependent on solvent polarity and the type of H-bond. A linear correlation of the absorption maximum of C120 with the solvent polarity function is revealed with the PCM model for all solvents except DMSO. The experimental absorption maximum of C120 in nine solvents is well described by a PCM–TDDFT scheme augmented with explicit inclusion of a few H-bonded solvent molecules, and quantitative agreement between our calculated results and experimental measurements is obtained with an average error of less than 2 nm. H-bonding at three different sites shifts the absorption wavelength of C120 either to the blue or to the red, that is, a significant role is played by solvent molecules in the first solvation shell in determining the electronic transition energy of C120. The dependence on the H-bonding site and solvent polarity is examined by using the Kamlet–Taft equation for solvatochromism.
Co-reporter:Wenwei Zhao, Wensheng Bian
Journal of Molecular Structure: THEOCHEM 2007 Volume 818(1–3) pp:43-49
Publication Date(Web):30 September 2007
DOI:10.1016/j.theochem.2007.05.002
Coumarins are well-known laser dyes in the blue-green region and studies on their electronic spectroscopy are important for understanding of their solvatochromic properties. A theoretical research of the various properties of the ground (S0) and first excited states (S1) of coumarin 6 in different solvents, including absorption and emission spectra, is presented here. Four isomers of coumarin 6 are investigated and compared. The excited-state geometries were optimized at the CIS level of theory whereas for the ground state, the HF and B3LYP levels of theory were applied. The geometric relaxation between the S0 and S1 states was examined and explained in terms of the nodal patterns of the highest occupied and lowest unoccupied molecular orbitals. The absorption and emission spectra in various solvents were calculated using the time-dependent density functional theory in combination with the polarized continuum model, and the results are in very good agreement with experimental measurements.
Co-reporter:Xiaojun Liu, Haidong Ju, Xian Zhao, Xutang Tao, Wensheng Bian, Minhua Jiang
Journal of Molecular Structure: THEOCHEM 2006 Volume 770(1–3) pp:73-77
Publication Date(Web):29 September 2006
DOI:10.1016/j.theochem.2006.05.023
The ground-state structure and electronic properties of a newly synthesized red fluorescent material, 2-[3-(2-{4-[(2-hydroxy-ethyl)-methyl-amino]-phenyl}-vinyl)-5, 5-dimethyl-cyclohex-2-enylidene]-malononitrile (A31), are investigated using a hybrid density-functional theory (DFT) approach, B3LYP, and the 6-31G* basis set. We have obtained four geometrical isomers. The theoretical infrared (IR) spectrum calculated by B3LYP/6-31G* level of theory is in very good agreement with our experimental measurement. The cation and anion are optimized to clarify the effects of the hole and electron injections and the energies needed by injections are estimated.
Co-reporter:Haitao Ma;Xiaojun Liu Dr.;Shijun Zheng ;Lingpeng Meng
ChemPhysChem 2006 Volume 7(Issue 8) pp:1786-1794
Publication Date(Web):3 AUG 2006
DOI:10.1002/cphc.200600183
Both the singlet(1A′) and triplet(3A′′) potential energy surfaces (PESs) of F+N3 reactions are investigated using the complete-active-space self-consistent field (CASSCF) and the multireference configuration interaction (MRCI) methods with a proper active space. The minimum energy crossing point (MECP) at the intersection seam between the 1A′ and 3A′′ PESs is located and used to clarify the reaction mechanisms. Two triplet transition states are found, with one in the cis form and the other one in the trans form. Further kinetic calculations are performed with the canonical unified statistical (CUS) theory on the singlet PES and the improved canonical variational transition-state (ICVT) method on the triplet PES. The rate constants are also reported. At 298 K, the calculated rate constant is in reasonably good agreement with experimental values, and spin–orbit coupling effects lower it by 28 %. The spectroscopic constants derived from the fitted potential-energy curves for the singlet and triplet states of NF are in very good agreement with experimental values. Our calculations indicate that the adiabatic reaction on the singlet PES leading to NF(a1Δ)+N2 is the major channel, whereas the nonadiabatic reaction through the MECP, which leads to NF(X3Σ−)+N2, is a minor channel.
Co-reporter:Wensha Xia, Mingkai Fu, Haitao Ma, Wensheng Bian
Chemical Physics (1–20 March 2017) Volumes 485–486() pp:29-34
Publication Date(Web):1–20 March 2017
DOI:10.1016/j.chemphys.2017.01.007
Co-reporter:Yinghui Ren, Bin Li and Wensheng Bian
Physical Chemistry Chemical Physics 2011 - vol. 13(Issue 6) pp:NaN2061-2061
Publication Date(Web):2010/12/24
DOI:10.1039/C0CP01186J
Full-dimensional quantum dynamics calculations of vinylidene–acetylene isomerization are performed and the state-specific resonance decay lifetimes of vinylidene(-d2) are computed. The theoretical scheme is a combination of several methods: normal coordinates are chosen to describe the nuclear motion of vinylidene, with both the parity and permutation symmetry exploited; phase space optimization in combination with physical considerations is used to generate an efficient discrete variable representation; the reaction coordinate is defined by us according to the three most relevant normal coordinates, along which a kind of optimal complex absorbing potential is imposed; the preconditioned inexact spectral transform method combined with an efficient preconditioner is employed to extract the energies and lifetimes of vinylidene. The overall computation is efficient. The computed energy levels generally agree with experiment well, and several state-specific lifetimes are reported for the first time.
