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Journal of Physical Chemistry. A

David R Hanson, Imanuel Bier, Baradan Panta, Coty N Jen, Peter H McMurry
Computational fluid dynamics simulations (CFD) of a flow reactor provided 3D spatial distributions of its temperature and flow profiles and abundances of sulfuric acid, nitrogeneous base and the acid-base clusters formed from them. Clusters were simulated via their kinetic formation and decomposition involving sulfuric acid and base molecules. Temperature and flow profiles and the base and sulfuric acid distributions are characterized and the latter is compared to mass spectrometer measurements. Concentrations of simulated clusters of sulfuric acid with either NH3 or dimethylamine were compared to experimentally measured particle concentrations...
April 28, 2017: Journal of Physical Chemistry. A
Putikam Raghunath, Yuan-Pern Lee, Ming-Chang Lin
The kinetics and mechanisms for the reaction of the Criegee intermediate CH2OO with HNO3 and the unimolecular decomposition of its reaction product CH2(O)NO3 are important in atmospheric chemistry. The potential-energy profile of the reactions predicted with the CCSD(T)/aug-cc-pVTZ//B3LYP/aug-cc-pVTZ method shows that the initial association yields a pre-reaction complex that isomerizes by H migration to yield excited intermediate nitrooxymethyl hydroperoxide NO3CH2OOH* with internal energy ~44 kcal mol(-1)...
April 28, 2017: Journal of Physical Chemistry. A
C Siouani, S Mahtout, S Safer, F Rabilloud
We systematically study the equilibrium geometries and electronic and magnetic properties of Gen+1 and VGen (n = 1-19) clusters using the density functional theory approach within the generalized gradient approximation. Endohedral structures in which the vanadium atom is encapsulated inside a Gen cage are predicted to be favored for n ≥ 10. The dopant V atom in the Gen clusters has not an immediate effect on the stability of small germanium clusters (n < 6), but it largely contributes to strengthen the stability for n ≥ 7...
April 28, 2017: Journal of Physical Chemistry. A
Adeayo O Ajala, Jun Shen, Piotr Piecuch
The previously developed active-space doubly electron-attached (DEA) equation-of-motion (EOM) coupled-cluster (CC) method with up to four-particle-two-hole (4p-2h) excitations [Shen, J.; Piecuch, P. J. Chem. Phys. 2013, 138, 194102], which utilizes the idea of applying a linear electron-attaching operator to the CC ground state of an (N - 2)-electron closed-shell system to generate ground and excited states of the N-electron open-shell species of interest, has been extended to a considerably less expensive model, in which both 3p-1h and 4p-2h terms rather than 4p-2h contributions only are selected using active orbitals...
April 28, 2017: Journal of Physical Chemistry. A
Qifan Liu, Zhuang Wu, Jian Xu, Yan Lu, Hongmin Li, Xiaoqing Zeng
Methylsulfoxide radicals CH3SOx (x = 1-4) are key reactive sulfur species (RSS) in the atmospheric oxidation of volatile organic sulfur compounds (VOSCs). Through flash vacuum pyrolysis (FVP) of trifluoromethanesulfinic acid methyl ester CF3S(O)OCH3 at 1000 K, the methoxysulfinyl radical CH3OSO has been generated in the gas phase and subsequently characterized in cryogenic N2, Ar, and Ne matrices by IR spectroscopy. Upon 266 nm laser irradiation, CH3OSO efficiently isomerizes to the less stable methylsulfonyl radical CH3SO2 in matrices without noticeable decomposition...
April 27, 2017: Journal of Physical Chemistry. A
Gourhari Jana, Sudip Pan, Pratim Kumar Chattaraj
The viability of a series of small gas molecules (H2, N2, CO, CO2, H2O, H2S, C2H2, CH4, CH3Cl, C2H4, and C2H6) bound [M-(bipy)](+) (bipy = bipyridyl; M = Cu, Ag, Au) complexes is investigated at the PBE0/cc-pVTZ/cc-pVTZ-PP level with a special emphasis on the possible bond activation within the bound ligands. While the bond dissociation energy, enthalpy change, and free energy change are computed to show the stability of the complexes with respect to the dissociation into [M-(bipy)]+ and free gas molecule (L), natural bond orbital, electron density, and energy decomposition analyses in conjunction with natural orbitals for chemical valence are carried out to characterize the nature of L-M bonds...
April 27, 2017: Journal of Physical Chemistry. A
Vladimir G Malkin, Olga L Malkina, Georgy M Zhidomirov
The close relation between the EPR hyperfine coupling constant and NMR indirect spin-spin coupling constant is well-known. For example, the Karplus-type dependence of hyperfine constants on the dihedral angle, originally proposed for NMR spin-spin coupling, is widely used in pNMR studies. In the present work we propose a new tool for visualization of hyperfine coupling pathways based on our experience with visualization of NMR indirect spin-spin couplings. The plotted 3D-function is the difference between the total electron densities when the magnetic moment of the nucleus of interest changes its sign and as such is an observable from the physical point of view...
April 27, 2017: Journal of Physical Chemistry. A
Sohidul Islam Mondal, Saumik Sen, Anirban Hazra, G Naresh Patwari
The homodimers of singly fluorine-substituted phenylacetylenes were investigated using electronic and vibrational spectroscopic methods in combination with density functional theory calculations. The IR spectra in the acetylenic C-H stretching region show a marginal red shift for the dimers relative to the monomers. Further, the marginal red shifts indicate that the acetylenic group in all the dimers is minimally perturbed relative to the corresponding monomer. The observed spectra were assigned to a set of π-stacked structures within an energy range of 1...
April 27, 2017: Journal of Physical Chemistry. A
Sándor Góbi, Alexandre Bergantini, Andrew M Turner, Ralf I Kaiser
Thin films of ammonium perchlorate (NH4ClO4) were exposed to energetic electrons at 5.5 K to explore the radiolytic decomposition mechanisms. The effects of radiolysis were monitored on line and in situ via Fourier-transform infrared spectroscopy (FTIR) in the condensed phase along with electron impact ionization quadrupole mass spectrometry (EI-QMS) and single-photon photoionization reflectron time-of-flight mass spectrometry (PI-ReTOF-MS) during the temperature programmed desorption (TPD) phase to probe the subliming molecules...
April 26, 2017: Journal of Physical Chemistry. A
Steve Scheiner
Receptors for halide anions are constructed based on the imidazolium unit, and then replacing the H-bonding C-H group first by halogen-bonding C-I and then by tetrel-bonding C-SnH3 and C-SiF3. Attaching a phenyl ring to any of these species has little effect on its ability to bind a halide, but incorporation of a second imidazolium to the benzene connector, forming a bidentate dicationic receptor, greatly enhances the binding. Addition of electron-withdrawing F atoms to each imidazolium adds a further increment...
April 26, 2017: Journal of Physical Chemistry. A
A D Squires, R A Lewis, Adam J Zaczek, Timothy M Korter
Through a combined experimental and theoretical investigation we determine that the fundamental modes of three quinacridones fall in the terahertz spectral range (1-10 THz, ∼30-300 cm(-1)). In each spectrum the terahertz resonances correspond to wagging, rocking, or twisting of the quinacridone rings, with the most intense absorption being an in-plane rocking vibration of the carbonyl oxygens. In spite of these spectral similarities, we demonstrate that terahertz measurements readily differentiate β-quinacridone, γ-quinacridone, and 2,9-dimethylquinacridone...
April 26, 2017: Journal of Physical Chemistry. A
Sönke Oswald, Mareike Wallrabe, Martin A Suhm
FTIR spectroscopy of supersonic expansions is used to characterize alcohol dimers with one, two, and several nitrogen molecules attached to them. The nitrogen coating causes progressive spectral downshifts of the OH stretching fundamentals which are related to and explain matrix isolation shifts. Comparison of methanol, tert-butyl alcohol and ethanol as well as deuteration of methanol assist in the assignment. Alcohol monomers and trimers are significantly more resistant to nitrogen coating due to a lack of cooperativity and dangling bonds, respectively...
April 26, 2017: Journal of Physical Chemistry. A
Dipali N Lande, Maneesha N Shewale, Shridhar P Gejji
Binding of novel endo-functionalized bis-urea/thiourea molecular receptors toward neutral 1,4-diazabicyclo[2.2.2]octane (DABCO) demonstrating stronger binding of the bis-thiourea macrocycles than their urea analogues by employing M06-2X/6-31+G(d,p) based density functional theory. The formation of such inclusion complexes is spontaneous, thermodynamically favorable and facilitated via the bifurcated N-H•••N•••H-N hydrogen bonding, C-H•••π, dipole-dipole and other non-covalent interactions, which reflect in the 'frequency shift' of their characteristic N-H vibrations in the calculated vibrational spectra of these complexes...
April 26, 2017: Journal of Physical Chemistry. A
Haamid Rasool Bhat, Prakash Chandra Jha
The anion binding selectivity and the recognition mechanism of two isomeric boranes namely 4-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline ([p-(Mes2B)C6H4(NMe3)]+, 1, where 'Mes' represents mesitylene and 'Me' represents methyl) and 2-[bis(2,4,6-trimethylphenyl)boranyl]-N,N,N-trimethylaniline ([o-(Mes2B)C6H4(NMe3)]+, 2) has been investigated using density functional theory (DFT) and time dependent-density functional theory (TD-DFT) methods. Natural population analysis indicates that the central boron atoms in 1 and 2 are the most active centers for nucleophilic addition of anions...
April 26, 2017: Journal of Physical Chemistry. A
Rubik Asatryan, Hayat Bennadji, Joseph W Bozzelli, Eli Ruckenstein, Lavrent Khachatryan
The fractional pyrolysis of lignin model compound para-coumaryl alcohol (p-CMA) containing a propanoid side chain and a phenolic OH group was studied using the System for Thermal Diagnostic Studies at temperatures from 200 to 900 °C, in order to gain mechanistic insight into the role of large substituents in high-lignin feedstocks pyrolysis. Phenol and its simple derivatives p-cresol, ethyl-, propenyl-, and propyl-phenols were found to be the major products predominantly formed at low pyrolysis temperatures (<500 °C)...
April 26, 2017: Journal of Physical Chemistry. A
George Schoendorff, Aaron C West, Michael W Schmidt, Klaus Ruedenberg, Angela K Wilson, Mark S Gordon
Valence virtual orbitals (VVOs) are a quantitative and basis set independent method for extracting chemically meaningful lowest unoccupied molecular orbitals (LUMOs). The VVOs are formed based on a singular value decomposition (SVD) with respect to precomputed and internally stored ab initio accurate atomic minimal basis sets (AAMBS) for the atoms. The occupied molecular orbitals and VVOs together form a minimal basis set that can be transformed into orthogonal oriented quasi-atomic orbitals (OQUAOs) that provide a quantitative description of the bonding in a molecular environment...
April 26, 2017: Journal of Physical Chemistry. A
Jin Shi, Wenlong Bi, Shenmin Li, Wenbo Dong, Jianmin Chen
Experiment and theoretical chemistry calculations were conducted to elucidate the mechanism of the reaction between 4-chlorobiphenyl (4-CB) and the NO3 radical. The degradation of PCBs was investigated mechanistically through transient absorption spectroscopy technology and high-accuracy theoretical calculation by using 4-CB as the model. Laser flash photolysis (LFP) experiments were performed at 355 nm. The main intermediate was analyzed through transient absorption spectroscopy and identified to be a charge transfer complex (CTC)...
April 26, 2017: Journal of Physical Chemistry. A
Hongbao Li, Andong Hu, Jun Jiang, Yi Luo
Extensive ab initio investigations have been performed to characterize the stable conformers of hydrated arginine (Arg-H2O). Many new low-energy canonical Arg-H2O conformers were identified and they are more stable than previous results. The large energy differences (more than 5.00 kcal mol(-1)) between the canonical and zwitterionic Arg-H2O isomers calculated by the composite CBS-QB3 method confirmed the dominance of the zwitterions. The micro effects of corrections of the zero-point energy and the basis set superposition error on the stability of hydrated isomers were carefully examined for the first time...
April 25, 2017: Journal of Physical Chemistry. A
Jessica Boreli Dos Reis Lino, Eduardo P Rocha, Teodorico Castro Ramalho
Quantum computing is the field of science that uses quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data. The fundamental information unit used in quantum computing is the quantum bit or qubit. It is well-known that quantum computers could theoretically be able to solve problems much more quickly than any classical computers. Currently, the first and still the most successful implementations of quantum information processing (QIP) have been based on nuclear spins in liquids...
April 25, 2017: Journal of Physical Chemistry. A
Kaiyuan Shen, Bingbing Suo, Wenli Zou
Potential energy curves of 65 and 147 low-lying Ω states of PtH and PtH(+) are respectively constructed using the multi-reference configuration interaction with singles, doubles, and Davidson's cluster corrections (MRCISD+Q), and the spin-orbit coupling effects are considered through the state-interaction approach with relativistic effective core potential spin-orbit operators. Spectroscopic constants fitted from these curves are reported and are compared with the available experimental or theoretical values...
April 25, 2017: Journal of Physical Chemistry. A
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