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Journal of Physical Chemistry. A

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https://www.readbyqxmd.com/read/29792704/double-hydrogen-atom-exchange-reactions-of-hx-x-f-cl-br-i-with-ho2
#1
Rex T Skodje, Jonathan R Church
A novel double hydrogen atom exchange process, HX+H'O2H'X+HO2 for the halogen series X=F, Cl, Br, and I, is identified using theoretical methods. These concerted reactions are mediated through a stabilized five-member planar ring transition state structure. The transition state barrier for the double exchange process is found to be significantly lower than that for the abstraction reaction of a single hydrogen atom, . Density functional theory employing the M11 exchange functional is used to compute parameters of the potential energy surface and the rate coefficients are obtained using transition state theory with small curvature tunneling...
May 24, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29792432/new-basis-set-for-the-evaluation-of-specific-rotation-in-flexible-biological-molecules-in-solution
#2
Angelika Baranowska-Laczkowska, Krzysztof Z Łączkowski, Christian Henriksen, Berta Fernandez
A detailed theoretical investigation of specific rotation is carried out in solution for nine flexible molecules of biological importance. Systematic search for the main conformers is followed by time-dependent density functional theory (TD-DFT) calculations of specific rotation employing a wide range of basis sets. Due to conformational flexibility of the compounds under study, the possibility of basis set size reduction without deterioration of the results is investigated. The increasing size (d-)aug-cc-pVXZ (X=D, T, Q) bases of Dunning et al...
May 24, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29792431/the-o-no-v-vibrational-relaxation-processes-revisited
#3
Pedro J S B Caridade, Jing Li, Vinícius C Mota, António J C Varandas
We have carried out a quasi-classical trajectory study of the $\mathrm{O}+\mathrm{NO}(v)$ energy transfer process using DMBE potential energy surfaces for the ground-states of the $^2A'$ and $^2A''$ manifolds. State-to-state vibrational relaxation rate constants have been computed over the temperature range $298\rm \,K$ and $3000\,\rm K$ and initial vibrational states between $v=1$ and 9. The momentum-Gaussian binning approach has been employed to calculate the probability of the vibrational transitions. A comparison of the calculated state-to-state rate coefficients with the results from experimental studies and previous theoretical calculations shows the relevance of the $1\,^2A''$ potential energy surface to the title vibrational relaxation process...
May 24, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29791159/reaction-kinetics-of-hydrogen-atom-abstraction-from-c4-c6-alkenes-by-the-hydrogen-atom-and-methyl-radical
#4
Quan-De Wang, Zi-Wu Liu
Alkenes are important ingredients of realistic fuels and are also critical intermediates during the combustion of a series of other fuels including alkanes, cycloalkanes and biofules. To provide insights into the combustion behavior of alkenes, detailed quantum chemical studies for crucial reactions are desired. Hydrogen abstractions of alkenes play a very important role in determining the reactivity of fuel molecules. This work is motivated by previous experimental and modeling evidences that current literature rate coefficients for the abstraction reactions of alkenes are still in need of refinement and/or re-determination...
May 23, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29791158/the-electronic-structure-of-ossi-calculated-by-ms-nevpt2-with-inclusion-of-the-relativistic-effects
#5
Bingbing Suo, Yongqin Lian, Wenli Zou, Yibo Lei
The electronic states of \ce{OsSi} are calculated by Multi-State N-Electron Valence State Second Order Perturbation Theory (MS-NEVPT2) with all-electron basis sets. The relativistic effects are considered comprehensively that allows us to identify the $X^{3}\Sigma^-_{0^+}$ ground state. The theoretical equilibrium bond length 2.103 {\AA} is close to the experimental measurement of 2.1207 {\AA} while the vibrational frequency 466 cm$^{-1}$ is smaller than the experimental value of 516 cm$^{-1}$. Two excited states, namely $^{3}\Pi_{1} (I)$ and $^{3}\Pi_1(II)$, are located at 15568 and 18316 cm$^{-1}$ above the ground state, respectively...
May 23, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29791157/a-novel-hybrid-correlation-energy-hyce-approach-based-on-separate-evaluations-of-internal-and-external-components
#6
Joseph Ivanic, Michael W Schmidt
A novel Hybrid Correlation Energy (HyCE) approach is proposed that determines the total correlation energy via distinct computation of its internal and external components. This approach evolved from two related studies. First, rigorous assessment of the accuracies and size extensivities of a number of electron correlation methods, that include perturbation theory (PT2), coupled-cluster (CC), configuration interaction (CI) and coupled electron pair approximation (CEPA), shows that the CEPA(0) variant of the latter and triples-corrected CC methods consistently perform very similarly...
May 23, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29791156/ab-initio-potential-energy-surfaces-of-c-3-collision-with-proton-and-quantum-dynamics-of-rotational-transition
#7
Sanchit Chhabra, Thogluva Janardhanan Dhilip Kumar
New ab initio potential energy surfaces have been generated for ground state and low-lying excited states of H+ + C3 system using the multi-reference conguration interaction (MRCI) method with Dunning's augmented correlation consistent polarized valence quadruple zeta (aug-cc-pVQZ) basis sets. The ground state and low-lying excited states show avoided crossing indicating non-adiabatic coupling. The anisotropy of the ground state surface has been analyzed by computing the multipolar expansion coefficients with the frozen C-C equilibrium bond length...
May 23, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29791155/deciphering-stability-of-five-membered-heterocyclic-radicals-balancing-act-between-delocalization-and-ring-strain
#8
Chitranjan Sah, Ajit Kumar Yadav, Sugumar Venkataramani
Computational studies on five membered heterocycles with single heteroatom and their isomeric dehydro-borole 1a-c, cyclopentadiene 2a-c, pyrrole 3a-c, furan 4b-c, phosphole 5a-c and thiophene 6b-c radicals have been carried out. Geometrical aspects through ground state electronic structures and stability aspects using bond dissociation energies (BDE) and radical stabilization energies (RSE) have been envisaged in this regard. Spin densities, electrostatic potentials (ESP) and natural bond orbital (NBO) analysis unveiled the extent of spin delocalization...
May 23, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29790334/correction-to-mechanism-of-the-ferrocyanide-iodate-sulfite-oscillatory-chemical-reaction
#9
Viktor Horváth, Irving R Epstein, Kenneth Kustin
No abstract text is available yet for this article.
May 23, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29786443/an-experimental-study-of-the-structural-effect-on-the-nanosecond-nonlinear-optical-response-of-o-doped-polycyclic-aromatic-hydrocarbons-pahs
#10
Ioannis Papadakis, Zoi Bouza, Aristeidis Stathis, Ioannis Orfanos, Stelios Couris, Tanja Miletić, Davide Bonifazi
The nonlinear optical response of some O-doped PAHs is systematically investigated in the present work aiming to understand the influence of structural effects on their nonlinear optical response. In that view, the third-order nonlinear optical properties of these PAHs were measured under 4 ns, visible (532 nm) and infrared (1064 nm) laser excitation. The O-doped PAHs were found exhibiting large saturable absorption and negative sign nonlinear refraction under visible excitation, both increasing with the addition of naphtalene units and with the number of O-atoms...
May 22, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29786434/ion-imaging-of-mgi-photofragment-in-ultraviolet-photodissociation-of-mass-selected-mg-ich-3-complex
#11
Kenichi Okutsu, Kenichiro Yamazaki, Motoyoshi Nakano, Keijiro Ohshimo, Fuminori Misaizu
We have observed images of MgI+ fragment ions produced in ultraviolet laser photodissociation of mass-selected Mg+ ICH3 ions at 266 nm. Split distribution almost perpendicular to the polarization direction of the photolysis laser was observed in the photofragment image. Potential energy curves of Mg+ ICH3 were obtained by theoretical calculations. Among these curves, the excited complex ion dissociated along almost repulsive potentials with several avoided crossings which was connected to MgI+ + CH3 . In the ground state of Mg+ ICH3 , the CH3 I was bonded with Mg from the iodine side, and the Mg-I-C bond angle was calculated to be 101...
May 22, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29782801/epr-evidence-of-liquid-water-in-ice-an-intrinsic-property-of-water-or-a-self-confinement-effect
#12
Muthulakshmi Thangswamy, Priya Maheshwari, Dhanadeep Dutta, Vinayak G Rane, Pradeep Kumar Pujari
Liquid water (LW) existence in pure ice below 273 K has been a controversial aspect primarily because of the lack of experimental evidences. Recently, electron paramagnetic resonance (EPR) has been used to study deeply supercooled water in a rapidly-frozen polycrystalline ice. The same technique can also be used to probe the presence of LW in polycrystalline ice that has formed through a more conventional, slow cooling one. In this context, the present study aims to emphasize that in case of an external probe involving techniques such as EPR, the results are influenced by the binary phase (BP) diagram of the probe-water system, which also predicts the existence of LW domains in ice, upto the eutectic point...
May 21, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29782168/rapid-aqueous-phase-hydrolysis-of-ester-hydroperoxides-arising-from-criegee-intermediates-and-organic-acids
#13
Ran Zhao, Christopher M Kenseth, Yuanlong Huang, Nathan F Dalleska, Xiaobi Michelle Kuang, Jierou Chen, Suzanne E Paulson, John H Seinfeld
Stabilized Criegee intermediates react with organic acids in the gas phase and at the air-water interface to form a class of ester hydroperoxides, α-acyloxyalkyl hydroperoxides (αAAHPs). A number of recent studies have proposed the importance of αAAHPs to the formation and growth of secondary organic aerosol (SOA). The chemistry of αAAHPs has not been investigated due to a lack of commercially available chemical standards. In this work, the behavior of αAAHPs in condensed phases is investigated for the first time...
May 21, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29781620/nonadiabatic-quantum-dynamics-with-frozen-width-gaussians
#14
Loic Joubert-Doriol, Artur F Izmaylov
We review techniques for simulating fully quantum nonadiabatic dynamics using the frozen-width moving Gaussian basis functions to represent the nuclear wavefunction. A choice of these basis functions is primarily motivated by the idea of the on-the-fly dynamics that will involve electronic structure calculations done locally in the vicinity of each Gaussian center and thus avoiding "curse of dimensionality'' appearing in large systems. For quantum dynamics involving multiple electronic states there are several aspects that need to be addressed...
May 21, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29781610/sulfur-speciation-in-biochars-by-very-high-resolution-benchtop-k%C3%AE-x-ray-emission-spectroscopy
#15
William Holden, Gerald T Seidler, Singfoong Cheah
The analytical chemistry of sulfur-containing materials poses substantial technical challenges, especially due to the limitations of 33S NMR and the time-intensive preparations required for wet-chemistry analyses. A number of prior studies have found that synchrotron-based x-ray absorption near edge structure (XANES) measurements can give detailed speciation of sulfur chemistry in such cases. However, due to the obvious access limitations, synchrotron XANES of sulfur cannot be part of routine analytical practice across the chemical sciences community...
May 21, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29781278/mechanisms-of-coupled-vibrational-relaxation-and-dissociation-in-carbon-dioxide
#16
Iole Armenise, Elena Kustova
A complete vibrational state-specific kinetic scheme describing dissociating carbon dioxide mixtures is proposed. CO2 symmetric, bending and asymmetric vibrations and dissociation-recombination are strongly coupled through inter-mode vibrational energy transfers. Comparative study of state-resolved rate coefficients is carried out; the effect of different transitions may vary considerably with temperature. A non-equilibrium 1-D boundary layer flow typical to hypersonic planetary entry is studied in the state-to-state approach...
May 21, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29776312/on-the-prospects-of-using-high-intensity-thz-pulses-to-induce-ultrafast-temperature-jumps-in-liquid-water
#17
Pankaj Kr Mishra, Vincent Bettaque, Oriol Vendrell, Robin Santra, Ralph Welsch
Ultrashort, high-intensity THz pulses, e.g., created at free-electron laser facilities, allow for direct investigation as well as the driving of intermolecular modes in liquids like water and thus will deepen our understanding of the hydrogen bonding network. In this work, the temperature-jump (T-jump) of water induced by THz radiation is simulated for ten different THz frequencies in the range from 3 to 30 THz and five different pulse intensities in the range from 1 × 1011 to 5 × 1012 W/cm2 employing both ab initio molecular dynamics (AIMD) and force field molecular dynamics (FFMD) approaches...
May 18, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29775306/mechanistic-study-on-water-splitting-reactions-by-small-silicon-clusters-si-3-x-x-si-be-mg-ca
#18
Tran Dieu Hang, Minh Tho Nguyen
(Abstract) Interaction, dissociation and dehydrogenation reactions of water monomer and dimer with pure and mixed tetrameric silicon clusters Si3X with X = Si, Be, Mg, Ca were investigated using high accuracy quantum chemical calculations. While geometries were optimized using the DFT/B3LYP functional with the aug-cc-pVTZ basis set, reaction energy profiles were constructed making use of the coupled-cluster theory with extrapolation to complete basis set, CCSD(T)/CBS. Cleavage of the O-H bond in water dimer is found to be more favored than that of water monomer in the reaction with Si4...
May 18, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29775062/near-infrared-fluorescence-from-in-plane-aromatic-cycloparaphenylene-dications
#19
Yui Masumoto, Naoyuki Toriumi, Atsuya Muranaka, Eiichi Kayahara, Shigeru Yamago, Masanobu Uchiyama
Cycloparaphenylenes (CPPs) are hoop-shaped conjugated hydrocarbons corresponding to partial structures of fullerenes or armchair carbon nanotubes. Here, we examined the fluorescence properties of a series of [n]cycloparaphenylene dications ([n]CPP2+, n = 5-9), which have unique in-plane aromaticity. The fluorescence peak positions of the [n]CPP2+s shifted to the longer-wavelength region with increasing ring size, reaching the near-infrared region for those with n > 5. The fluorescence quantum yield of [6]CPP2+ was the highest among the [n]CPP2+s examined in this study, and the value was of the same order as that of carbon nanotubes...
May 18, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29775056/the-electronic-structure-of-beryllium-chains
#20
Ahmad W Huran, Nadia Ben Amor, Stefano Evangelisti, Sophie Hoyau, Thierry Leininger, Veronique Brumas
The electronic structure of quasi one-dimensional Beryllium chains, BeΝ has been theoretically studied at an ab initio level for N=3,4,...,12. In particular, linear and cyclic systems have been compared by using high-quality Coupled-Cluster formalisms. Both linear and cyclic species have been found to be local minima on the corresponding Potential-Energy Surface, for all the considered values of N. The linear geometry is the most stable one only in the case of Be4 , while the cyclic geometry is preferred for N>4...
May 18, 2018: Journal of Physical Chemistry. A
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