Zheng-Wen Long

Theoretical studies on reactions of the stabilized H2COO with HO2 and the HO2···H2O complex.

The reactions of H(2)COO with HO(2) and the HO(2)···H(2)O complex are studied by employing the high-level quantum chemical calculations with B3LYP and CCSD(T) theoretical methods, the conventional transition-state theory (CTST), and the Rice-Ramsperger-Kassel-Marcus (RRKM) with Eckart tunneling correction. The calculated results show that the proton transfer plus the addition reaction channel (TS1A) is preferable for the reaction of H(2)COO with HO(2) because the barriers are -10.8 and 1.6 kcal/mol relative to the free reactants and the prereactive complex, respectively, at the CCSD(T)/6-311++G(3df,2p)//B3LYP/6-311++G(d,p) level of theory. Furthermore, the rate constant via TS1A (2.23 × 10(-10) cm(3) molecule(-1) s(-1)) combined with the concentrations of the species in the atmosphere demonstrates that the HO(2) radical would be the dominant sink of H(2)COO in some areas, where the concentration of water is less than 10(17) molecules cm(-3). In addition, although the single water molecule would lower the activated barrier of TS1A from 1.0 to 0.1 kcal/mol with respect to the respective complexes, the rate constant is lower than that of the reaction of HO(2) with H(2)COO.

Formic acid catalyzed gas-phase reaction of H2O with SO3 and the reverse reaction: a theoretical study.

The formic acid catalyzed gas-phase reaction between H(2)O and SO(3) and its reverse reaction are respectively investigated by means of quantum chemical calculations at the CCSD(T)//B3LYP/cc-pv(T+d)z and CCSD(T)//MP2/aug-cc-pv(T+d)z levels of theory. Remarkably, the activation energy relative to the reactants for the reaction of H(2)O with SO(3) is lowered through formic acid catalysis from 15.97 kcalu2009 mol(-1) to -15.12 and -14.83 kcalu2009 mol(-1) for the formed H(2)O⋅⋅⋅SO(3) complex plus HCOOH and the formed H(2)O⋅⋅⋅HCOOH complex plus SO(3), respectively, at the CCSD(T)//MP2/aug-cc-pv(T+d)z level. For the reverse reaction, the energy barrier for decomposition of sulfuric acid is reduced to -3.07 kcalu2009 mol(-1) from 35.82 kcalu2009 mol(-1) with the aid of formic acid. The results show that formic acid plays a strong catalytic role in facilitating the formation and decomposition of sulfuric acid. The rate constant of the SO(3)+H(2)O reaction with formic acid is 10(5) times greater than that of the corresponding reaction with water dimer. The calculated rate constant for the HCOOH+H(2)SO(4) reaction is about 10(-13) cm(3) u2009molecule(-1) u2009s(-1) in the temperature range 200-280 K. The results of the present investigation show that formic acid plays a crucial role in the cycle between SO(3) and H(2)SO(4) in atmospheric chemistry.

Theoretical Study on the Gas Phase Reaction of Sulfuric Acid with Hydroxyl Radical in the Presence of Water

The reactions of H2SO4 with the OH radical without water and with water are investigated employing the quantum chemical calculations at the B3LYP/6-311+G(2df,2p) and MP2/aug-cc-pv(T+d)z levels of theory, respectively. The calculated results show that the reaction of H2SO4 with OH and H2O is a very complex mechanism because of the formation of the prereactive complex prior to the transition state and product. There are two prereactive complexes with stabilization energies being -20.28 and -20.67 kcal/mol, respectively. In addition, the single water can lower the energy barriers of the hydrogen abstraction and the proton transfer to 7.51 and 6.37 kcal/mol, respectively from 13.79 and 8.82 kcal/mol with respect to the corresponding prereactive complex. The computed rate constants indicate that the water-assisted reaction of sulfuric acid with OH radical is of greater importance than the reaction of the naked sulfuric acid with the OH radical because the rate constant of the water-assisted process is about 10(3) faster than that of the reaction sulfuric acid with OH. Therefore, the conclusion is obtained that the water-assisted process plays an important role in the sink for the gaseous sulfuric acid in the clean area.

Theoretical studies on gas-phase reactions of sulfuric acid catalyzed hydrolysis of formaldehyde and formaldehyde with sulfuric acid and H2SO4···H2O complex.

The gas-phase reactions of sulfuric acid catalyzed hydrolysis of formaldehyde and formaldehyde with sulfuric acid and H2SO4···H2O complex are investigated employing the high-level quantum chemical calculations with M06-2X and CCSD(T) theoretical methods and the conventional transition state theory (CTST) with Eckart tunneling correction. The calculated results show that the energy barrier of hydrolysis of formaldehyde in gas phase is lowered to 6.09 kcal/mol from 38.04 kcal/mol, when the sulfuric acid is acted as a catalyst at the CCSD(T)/aug-cc-pv(T+d)z//M06-2X/6-311++G(3df,3pd) level of theory. Furthermore, the rate constant of the sulfuric acid catalyzed hydrolysis of formaldehyde combined with the concentrations of the species in the atmosphere demonstrates that the gas-phase hydrolysis of formaldehyde of sulfuric acid catalyst is feasible and could be of great importance for the sink of formaldehyde, which is in previously forbidden hydrolysis reaction. However, it is shown that the gas-phase reactions of formaldehyde with sulfuric acid and H2SO4···H2O complex lead to the formation of H2C(OH)OSO3H, which is of minor importance in the atmosphere.

New insights in atmospheric acid-catalyzed gas phase hydrolysis of formaldehyde: a theoretical study

The gas phase hydrolysis of HCHO catalyzed via nitric acid and acetic acid, the typical atmospheric acids has been theoretically investigated using M06-2X, CCSD(T), and CCSD(T)-F12A theoretical methods using the 6-311++G(d,p), aug-cc-pVTZ, and VTZ-F12 basis sets and utilizing transition state theory. Our studies predict that when the HNO3 or CH3COOH and HCHO⋯H2O act as reactants, the reactions occur in one step, whereas the reactions of HNO3⋯H2O or CH3COOH⋯H2O with HCHO proceed via a two-step mechanism. Our results also show that the free energy barrier of the gas phase hydrolysis of HCHO assisted by HNO3 or CH3COOH is reduced to 13.95 or 14.27 kcal mol−1 relative to the respective pre-reactive complex from 40.23 kcal mol−1 in the naked HCHO + H2O reaction. The calculated kinetic data suggests that the HCHO + HNO3⋯H2O entrance channel with a two-step mechanism is 1.84–2.76 times faster than HNO3 + HCHO⋯H2O with a one-step mechanism, whereas the HCHO⋯H2O + CH3COOH entrance path is significantly more favorable than that of HCHO + CH3COOH⋯H2O, in the temperature range of 200–300 K. The reaction rates of the gas phase hydrolysis of HCHO catalyzed by HNO3 or CH3COOH are much slower than that of the gas phase reaction of HCHO with an OH radical, which demonstrates that the contributions of both catalytic reactions are of minor importance for the sink of HCHO in gas-phase atmospheric chemistry. However, the new findings in this investigation are not only of great necessity and importance for elucidating the gas phase hydrolysis of formaldehyde, but are also of great interest for understanding the importance of other carbonyl compounds in the atmosphere.

Theoretical Study on Impact of Single Water Molecule on OH+O3 Reaction

Quantum chemical calculations are performed to study the reactions of OH and ozone without and with water to estimate whether the single water molecule can decrease the energy barrier of the OH radical reaction with ozone. The calculated results demonstrate that the single water molecule can reduce the activated barrier of the naked OH+O3 reaction with the value of about 4.18 kJ/mol. In addition, the transition state theory is carried out to determine whether the single water molecule could enhance the rate constant of the OH+O3 reaction. The computed kinetic data indicate that the rate of the ozone reaction with the formed complexes between OH and water is much slower than that of the OH+O3 reaction, whereas the rate constant of OH reaction with the formed H2O···O3 complex is 2 times greater than that of the naked OH radical with ozone reaction. However, these processes in the atmosphere are not important because the reactions can not compete well with the naked reaction of OH with ozone under atmospheric condition.

Quantum speed limit for a relativistic electron in the noncommutative phase space

The influence of the noncommutativity on the average speed of a relativistic electron interacting with a uniform magnetic field within the minimum evolution time is investigated. We find that it is possible for the wave packet of the electron to travel faster than the speed of light in vacuum because of the noncommutativity. It suggests that due to the noncommutativity, Lorentz invariance is violated in the relativistic quantum mechanics region.

Comparative study on the spectral properties of boron clusters Bn0/−1(n = 38–40)

The all-boron fullerenes B40−1 and B39−1 discovered in recent experiments are characterized and revealed using photoelectron spectroscopy. Except for the photoelectron spectroscopy, one may identify such boron clusters with other spectroscopic techniques, such as infrared spectra and Raman spectra. Insight into the spectral properties of boron clusters is important to understand the boron clusters and find their potential applications. In this work, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are carried out to comparatively study the vibrational frequencies, infrared spectra, Raman spectra and electronic absorption spectra of boron clusters Bn0/−1(nu2009=u200938–40). The numerical simulations show that such boron clusters have different and meaningful spectral features. These spectral features are readily compared with future spectroscopy measurements and can be used as fingerprints to distinguish the boron clusters Bn0/−1 with different structures (cage structure or quasi-planar structure) and with different sizes (nu2009=u200938–40).

Structures, stabilities and spectral properties of borospherene B 44 − and metalloborospherenes MB 44 0/− (M = Li, Na, and K)

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are carried out to study the stabilities, photoelectron, infrared, Raman and electronic absorption spectra of borospherene B44− and metalloborospherenes MB440/− (Mu2009=u2009Li, Na, and K). It is found that all atoms can form stable exohedral metalloborospherenes M&B440/−, whereas only Na and K atoms can be stably encapsulated inside B440/− cage. In addition, relative energies of these metalloborospherenes suggest that Na and K atoms favor exohedral configuration. Importantly, doping of metal atom can modify the stabilities of B44 with different structures, which provides a possible route to produce stable boron clusters or metalloborospherenes. The calculated results suggest that B44 tends to get electrons from the doped metal. Metalloborospherenes MB44− are characterized as charge-transfer complexes (M2+B442−), where B44 tends to get two electrons from the extra electron and the doped metal, resulting in similar features with anionic B442−. In addition, doping of metal atom can change the spectral features, such as blueshift or redshift and weakening or strengthening of characteristic peaks, since the extra metal atom can modify the electronic structure. The calculated spectra are readily compared with future spectroscopy measurements and can be used as fingerprints to identify B44− and metalloborospherenes.

Experimental and Theoretical Study of Reactions of OH Radicals with Hexenols: An Evaluation of the Relative Importance of the H-Abstraction Reaction Channel.

C6 hexenols are one of the most significant groups of volatile organic compounds with biogenic emissions. The lack of corresponding kinetic parameters and product information on their oxidation reactions will result in incomplete atmospheric chemical mechanisms and models. In this paper, experimental and theoretical studies are reported for the reactions of OH radicals with a series of C6 hexenols, (Z)-2-hexen-1-ol, (Z)-3-hexen-1-ol, (Z)-4-hexen-1-ol, (E)-2-hexen-1-ol, (E)-3-hexen-1-ol, and (E)-4-hexen-1-ol, at 298 K and 1.01 × 10(5) Pa. The corresponding rate constants were 8.53 ± 1.36, 10.1 ± 1.6, 7.86 ± 1.30, 8.08 ± 1.33, 9.10 ± 1.50, and 7.14 ± 1.20 (in units of 10(-11) cm(3) molecule(-1) s(-1)), respectively, measured by gas chromatography with a flame ionization detector (GC-FID), using a relative technique. Theoretical calculations concerning the OH-addition and H-abstraction reaction channels were also performed for these reactions to further understand the reaction mechanism and the relative importance of the H-abstraction reaction. By contrast to previously reported results, the H-abstraction channel is a non-negligible reaction channel for reactions of OH radicals with these hexenols. The rate constants of the H-abstraction channel are comparable with those for the OH-addition channel and contribute >20% for most of the studied alcohols, even >50% for (E)-3-hexen-1-ol. Thus, H-abstraction channels may have an important role in the reactions of these alcohols with OH radicals and must be considered in certain atmospheric chemical mechanisms and models.