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Journal of Physical Chemistry. A

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https://www.readbyqxmd.com/read/28334538/modelling-studies-of-inhomogeneity-effects-during-laser-flash-photolysis-experiments-a-reaction-diffusion-approach
#1
Eva Doka, Gabor Lente
This works present a rigorous mathematical study of the effect of unavoidable inhomogeneities in laser flash photolysis experiments. There are two different kinds of inhomegenities: the first arises from diffusion, whereas the second one has geometric origins (the shapes of the excitation and detection light beams). Both of these are taken into account in our reported model, which gives rise to a set of reaction-diffusion type partial differential equations. These equations are solved by a specially developed finite volume method...
March 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28333464/quantification-of-thermodynamic-hydridicity-of-hydride-complexes-of-mn-re-mo-and-w-using-molecular-electrostatic-potential
#2
Sandhya Karakkadparambil Sankaran, Cherumuttathu H Suresh
Molecular electrostatic potential (MESP) at the hydride nucleus, VH is proposed as a powerful measure of the hydride donor ability (hydridicity) of metal hydride complexes. The VH alues are determined for several group VI and group VII octahedral metal hydride complexes of Mo, W, Mn and Re at the B3LYP level of DFT. Further, the hydridicity, defined by the thermodynamic parameter ΔG(o)H- is determined for all these complexes using a thermodynamic cycle which describes the hydride abstraction reaction by H3O(+) ion...
March 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28332401/ultrafast-excited-state-dynamics-of-cytosine-aza-derivative-and-analogues
#3
Zhongneng Zhou, Xueyao Zhou, Xueli Wang, Bin Jiang, Yongle Li, Jinquan Chen, Jianhua Xu
Excited state dynamics of 5-azacytosine (5-AC), 2,4-diamino-1,3,5-triazine (2,4-DT), and 2-amino-1,3,5-triazine (2-AT) were comprehensively investigated with steady state absorption, fluorescence and femtosecond transient absorption measurements. Time-dependent density functional theory (TDDFT) calculations were performed to help assign the absorption bands and understand the excited state decay mechanisms. The experimental results of excited singlet state dynamics for 5-AC, 2,4-DT and 2-AT with femtosecond time resolution were reported for the first time...
March 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28287725/representing-global-reactive-potential-energy-surfaces-using-gaussian-processes
#4
Brian Kolb, Paul Marshall, Bin Zhao, Bin Jiang, Hua Guo
Representation of multidimensional global potential energy surfaces suitable for spectral and dynamical calculations from high-level ab initio calculations remains a challenge. Here, we present a detailed study on constructing potential energy surfaces using a machine learning method, namely, Gaussian process regression. Tests for the (3)A″ state of SH2, which facilitates the SH + H ↔ S((3)P) + H2 abstraction reaction and the SH + H' ↔ SH' + H exchange reaction, suggest that the Gaussian process is capable of providing a reasonable potential energy surface with a small number (∼1 × 10(2)) of ab initio points, but it needs substantially more points (∼1 × 10(3)) to converge reaction probabilities...
March 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28281756/aromaticity-of-peri-and-para-substituted-naphthalene-1-carbaldehyde-comparison-with-1-nitronaphthalene
#5
Irena Majerz, Teresa Dziembowska
Aromaticity of the naphthalene ring substituted by formyl or nitro and secondary amine groups in peri and para positions has been investigated. HOMA (harmonic oscillator model of aromaticity) index of the naphthalene rings has been used to characterize the aromaticity of the investigated molecules. Ellipticity of C2-C3 (C6-C7) bonds, obtained by means of topological analysis of the electron density, has been used as a measure of the through-resonance effect between the para substituents. Dependence of the HOMA values on the rotation angle of formyl and nitro groups to the aromatic plane for naphthalene-1-carbaldehyde and their derivatives with dimethylamino group in para position has been analyzed...
March 23, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28328211/the-water-solvent-effect-on-theoretical-evaluation-of-1h-nmr-chemical-shifts-the-o-methyl-inositol-isomer
#6
Helio F Dos Santos, Marcelo Chagas, Leonardo De Souza, Willian Rocha, Mauro V De Almeida, Cleber P A Anconi, Wagner Batista De Almeida
In this paper, density functional theory calculations of nuclear magnetic resonance (NMR) chemical shifts for L-quebrachitol isomer, previously studied in our group (Mag. Res. Chem. 50 (2012) 608-614) are reported aiming to investigate in more details the water solvent effect on the prediction of 1H NMR spectra. In order to include explicit water molecules, twenty water-L-quebrachitol configurations obtained from Monte Carlo simulation were selected to perform geometry optimizations using the effective fragment potential method encompassing 60 water molecules around the solute...
March 22, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28328203/a-physical-molecular-mechanics-method-for-damped-dispersion
#7
Pragya Verma, Bo Wang, Laura E Fernandez, Donald G Truhlar
Damped dispersion can be a significant component of the interaction energy in many physical and chemical processes, for example, physisorption and noncovalent complexation. For physically interpreting and modeling such processes, it is convenient to have an analytic method to calculate damped dispersion that is readily applicable across the entire periodic table. Of the available methods to calculate damped dispersion energy for interacting systems with overlapping charge distributions, we select symmetry-adapted perturbation theory (SAPT) as providing a reasonable definition, and of the possible analytic forms, we choose the D3(BJ) method...
March 22, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28326780/correction-to-origin-of-substituent-effect-on-tautomeric-behavior-of-1-2-4-triazole-derivatives-combined-spectroscopic-and-theoretical-study
#8
Tetiana Sergeieva, Maria Bilichenko, Sergiy Holodnyak, Yulia V Monaykina, Sergiy I Okovytyy, Sergiy I Kovalenko, Eugene Voronkov, Jerzy Leszczynski
No abstract text is available yet for this article.
March 22, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28281759/application-of-the-transpiration-method-to-determine-the-vapor-pressure-and-related-physico-chemical-data-of-low-volatile-thermolabile-and-toxic-organo-thio-phosphates
#9
Marc A Althoff, Kathrin Grieger, Martin A C Härtel, Konstantin L Karaghiosoff, Thomas M Klapötke, Manfred Metzulat
The present work represents the most recent study on the physico-chemical properties of the organophosphate compound class being directly related to the Chemical Weapons Convention (CWC). This compound class is of great importance in the ongoing conflict in Syria. Here, the vapor pressure of the deadly organo(thio)phosphate Amiton and seven of its derivatives was investigated. These medium to low volatile analytes pose a potential threat toward human life by inhalation or direct contact with the skin at very low doses...
March 22, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28323432/electronic-structures-and-oh-induced-atmospheric-degradation-of-cf3nsf2-a-potential-green-dielectric-replacement-for-sf6
#10
Lin Cheng, Xiaojuan Yu, Kun Zhao, Hua Hou, Baoshan Wang
Electronic structures of Trifluoromethyl imionosulfur difluoride (CF3NSF2) and degradation mechanisms by hydroxyl radical have been investigated using density functional theory (M06-2X), the complete basis set quadratic CBS-Q, and the explicitly correlated coupled-cluster methods [CCSD(T)-F12]. The d-function augmented Correlation-consistent basis sets including triple- and quadruple- were employed for the sulfur-containing species. It was found that CF3NSF2 exists as two conformations connected by the internal rotation of CF3 around the central NS bond...
March 21, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28322555/photophysical-dynamics-and-relaxation-pathways-of-ligand-to-metal-charge-transfer-states-in-the-5f-1-np-vi-o2cl4-2-anion
#11
Beau J Barker, John M Berg, Stosh A Kozimor, Nicholas R Wozniak, Marianne P Wilkerson
Although several publications report on the electronic structure of the neptunyl ion, experimental measurements to detail the photophysical dynamics of this open-shell actinyl system are limited in number. Time-resolved photoluminescence has been a useful experimental approach for understanding photophysical dynamics and relaxation pathways of a variety of other molecular and ionic systems, including gaseous plutonium hexafluoride and solid-state uranyl compounds. Here, we investigate time-resolved photoluminescence emission of the 5f(1) neptunyl tetrachloride ([Np(VI)O2Cl4](2-)) dianion following visible excitation...
March 21, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28290699/toward-the-classical-description-of-halogen-bonds-a-quantum-based-generalized-empirical-potential-for-fluorine-chlorine-and-bromine
#12
Lucas A Santos, Elaine F F da Cunha, Teodorico C Ramalho
The electronic effects in supramolecular systems are a great challenge for computational chemistry, and the understanding of ligand-protein interactions driven by halogen bonds can be limited by molecular mechanics point of view. In fact, the variations of the halogen bond acceptors, such as an aromatic ring and electrons lone pairs, restrict the classical approximations even more. Our work enhances the statement that halogen bonds are led mainly by orbital interactions via σ*C-X. Nonetheless, we have pointed a straight relationship between the maximum ESP value on the σ-hole and the LUMO energy levels of the halogen bond donor...
March 21, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28267347/structural-evolution-of-gold-clusters-aun-n-21-25-revisited
#13
Navneet Singh Khetrapal, Satya S Bulusu, Xiao Cheng Zeng
We performed a combined theoretical and experimental photoelectron spectroscopy study of the structural evolution of gold anion clusters Aun(-) in the size range n = 21-25, a special size range for gold anion clusters where extensive structural changes from the pyramidal structure at Au20(-) toward the core-shell structure at Au26(-) were expected to occur. Density functional theory calculations with inclusion of spin-orbit effects were employed to produce the simulated spectra for the selected low-energy isomers obtained from basin-hopping global minimum search...
March 21, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28319388/visualizing-intramolecular-vibrational-redistribution-in-cyclotrimethylene-trinitramine-rdx-crystal-by-multiplex-coherent-anti-stokes-raman-scattering
#14
Guoyang Yu, Yangyang Zeng, Wencan Guo, Honglin Wu, Gangbei Zhu, Zhaoyang Zheng, Xianxu Zheng, Yunfei Song, Yanqiang Yang
The femtosecond time-resolved multiplex coherent anti-Stokes Raman scattering (CARS) technique has been performed to investigate the intramolecular vibrational redistribution (IVR) through vibrational couplings in RDX molecules. In the multiplex CARS experiment, the supercontinuum (SC) was used as broadband Stokes light to coherently and collectively excite multiple vibrational modes, and quantum beats arising from vibrational couplings among these modes were observed. The IVR of RDX is visualized by a topological graph of these vibrational couplings...
March 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28319387/temperature-dependence-in-the-terahertz-spectrum-of-nicotinamide-anharmonicity-and-hydrogenbonded-network
#15
Masae Takahashi, Nubuyuki Okamura, Xinyi Fan, Hitoshi Shirakawa, Hiroaki Minamide
We have investigated the terahertz-spectral property of nicotinamide focusing on the temperature dependence in the range of 14 to 300 K. We observed that almost all peaks in the terahertz spectrum of the nicotinamide crystal showed a remarkable shift with temperature, whereas the lowest-frequency peak at 34.8 cm-1 showed a negligible shift with temperature. By analyzing the terahertz spectrum with the dispersion-corrected density-functional-theory calculations, we found that the difference in the temperature dependence of the peak shift is well understood in terms of the presence/absence of stretching vibration of the intermolecular hydrogen bond in the mode and the change of cell parameters...
March 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28319385/structural-and-electronic-properties-of-transition-metal-oxides-attached-to-a-single-walled-cnt-as-a-lithium-ion-battery-electrode-a-first-principles-study
#16
Liew Weng Tack, Mohd Asyadi Azam, Raja Noor Amalina Raja Seman
Single-walled carbon nanotubes (SWCNTs) and metal oxides (MOs), such as manganese (IV) oxide (MnO2), cobalt (II, III) oxide (Co3O4), and nickel (II) oxide (NiO) hybrid structures, have received great attention because of their promising application in lithium-ion batteries (LIBs). As electrode materials for LIBs, the structure of SWCNT/MOs provides high power density, good electrical conductivity, and excellent cyclic stability. In this work, first-principles calculations were used to investigate the structural and electronic properties of MOs attached to (5, 5) SWCNT and Li-ion adsorption to SWCNT/ metal oxide composites as electrode materials in LIBs...
March 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28319383/molecular-docking-towards-panchromatic-dye-sensitizers-for-solar-cells-based-upon-tetraazulenylporphyrin-and-tetraanthracenylporphyrin
#17
Cai-Rong Zhang, Xing-Yu Li, Yu-Lin Shen, Youzhi Wu, Zi-Jiang Liu, Hongshan Chen
Novel dye sensitizers are highly expected in the development of dye-sensitized solar cells (DSSCs) since dye sensitizers can significantly affect the power conversion efficiency (PCE). Here, the molecular docking strategy is applied to design panchromatic dye sensitizers for DSSCs in order to improve light-harvesting efficiency covering the full solar spectrum. Considering the broad absorption bands of tetraanthracenylporphyrins (TAnPs) and tetraazuleneporphyrins (TAzPs), based upon porphyrin dye sensitizer YD2-o-C8, the panchromatic dye sensitizers coded as H2(TAnP)-α, H2(TAzP)-γ, H2(TAzP)-ε, and H2(TAzP)-δ are designed by the substitution of the porphyrin-ring in YD2-o-C8 with TAnPs and TAzPs moieties at different positions...
March 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28319381/effects-of-second-metal-al-v-co-doping-on-the-no-reactivity-of-small-rhodium-cluster-cations
#18
Shinichi Hirabayashi, Masahiko Ichihashi
Reactions of pure and doped rhodium cluster cations, RhnX(+) (n = 2-6; X = Al, V, Co, Rh), with NO molecules were investigated at near-thermal energy using a guided ion beam tandem mass spectrometer. We found that the doping with Al and V increases the total reaction cross section mostly. Under single collision conditions, Rh2X(+) react with NO to produce Rh2N(+) with releasing metal monoxide, XO, while RhnX(+) (n = 3-6) adsorb NO. For the specific clusters, RhnAl(+) (n = 3 and 4) and RhnV(+) (n = 4-6), the NO adsorption is often accompanied with the release of one Rh atom...
March 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28319378/computational-study-of-13c-nmr-csa-patterns-in-c20h10-and-c20h10-4-insights-into-their-variation-upon-planarization-and-formation-of-concentric-aromatic-species-in-the-smaller-isolated-pentagon-structural-motif
#19
Alvaro Muñoz-Castro, Wilson Caimanque-Aguilar, Cesar Morales-Verdejo
Corannulene, C20H10, exhibits a concave surface in the ground state which is able to experience a bowl-to-bowl inversion through a planar conformation. Such structure is the smaller example resembling an isolated-pentagon motif, as a relevant fragment in Fullerene chemistry. Here, we explored the differences between bowl and planar conformations involving both energetic and 13C-NMR properties, for the neutral and tetraanionic species by using DFT methods. This allows to understand the variation of the chemical environment at the carbon atoms upon planarization of this representive motif...
March 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28319375/dissociative-photoionization-of-dimethyl-carbonate-the-more-it-is-cut-the-bigger-the-fragment-ion
#20
Xiangkun Wu, Xiaoguo Zhou, Patrick Hemberger, Andras Bodi
The dissociation of internal energy selected dimethyl carbonate (DMC) cations was studied by imaging photoelectron photoion coincidence spectroscopy (iPEPICO) in the 10.3-12.5 eV photon energy range. Vibrational fine structure is observed in the ground state band of the threshold photoelectron spectrum up to the dissociation threshold, and Franck-Condon simulations identify the O-C-O bend mode, in particular in combination with the C=O stretch mode, to be active. The DMC ionization energy was determined to be 10...
March 20, 2017: Journal of Physical Chemistry. A
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