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  Subjects -> CHEMISTRY (Total: 767 journals)
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CHEMISTRY (532 journals)            First | 1 2 3 4 5 6 | Last

Graphene     Open Access   (Followers: 10)
Green and Sustainable Chemistry     Open Access   (Followers: 3)
Green Chemistry Letters and Reviews     Open Access   (Followers: 4)
Green Processing and Synthesis     Full-text available via subscription   (Followers: 1)
Handbook of Exploration and Environmental Geochemistry     Full-text available via subscription   (Followers: 1)
Handbook of Exploration Geochemistry     Full-text available via subscription  
Handbook of Surface Science     Full-text available via subscription   (Followers: 2)
Handbook of Vapor Pressure     Full-text available via subscription  
Helvetica Chimica Acta     Hybrid Journal   (Followers: 9)
Heritage Science     Open Access   (Followers: 1)
Heteroatom Chemistry     Hybrid Journal   (Followers: 2)
High Energy Chemistry     Hybrid Journal  
Indian Chemical Engineer     Hybrid Journal   (Followers: 3)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 12)
Indian Journal of Chemistry - Section B (IJC-B)     Open Access   (Followers: 5)
Indian Journal of Natural Products and Resources (IJNPR)     Open Access   (Followers: 3)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 9)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 4)
Inorganic Chemistry     Full-text available via subscription   (Followers: 19)
Inorganic Chemistry Communications     Hybrid Journal   (Followers: 7)
Inorganic Materials     Hybrid Journal   (Followers: 2)
Inorganica Chimica Acta     Hybrid Journal   (Followers: 4)
Instrumentation Science & Technology     Hybrid Journal   (Followers: 3)
International Archives of Science and Technology     Open Access  
International Journal for Ion Mobility Spectrometry     Hybrid Journal   (Followers: 1)
International Journal of Adhesion and Adhesives     Hybrid Journal   (Followers: 12)
International Journal of Bioassays     Open Access   (Followers: 5)
International Journal of Biological and Chemical Sciences     Open Access   (Followers: 2)
International Journal of Biological Chemistry     Open Access   (Followers: 4)
International Journal of Biomedical Nanoscience and Nanotechnology     Hybrid Journal   (Followers: 5)
International Journal of Carbohydrate Chemistry     Open Access   (Followers: 7)
International Journal of Chemical and Analytical Science     Full-text available via subscription   (Followers: 2)
International Journal of Chemical and Life Sciences     Open Access   (Followers: 3)
International Journal of Chemical Kinetics     Hybrid Journal   (Followers: 4)
International Journal of Chemical Technology     Open Access   (Followers: 3)
International Journal of Chemistry     Open Access   (Followers: 7)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Corrosion     Open Access   (Followers: 10)
International Journal of High Throughput Screening     Open Access   (Followers: 2)
International Journal of Medicinal Chemistry     Open Access   (Followers: 7)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 7)
International Journal of Molecular Imaging     Open Access   (Followers: 1)
International Journal of Molecular Sciences     Open Access   (Followers: 1)
International Journal of Nano Dimension     Open Access  
International Journal of Nonferrous Metallurgy     Open Access  
International Journal of Photoenergy     Open Access   (Followers: 2)
International Journal of Physical Sciences     Open Access  
International Journal of Spray and Combustion Dynamics     Full-text available via subscription   (Followers: 6)
International Journal of Tryptophan Research     Open Access  
Iranian Polymer Journal     Hybrid Journal   (Followers: 4)
Israel Journal of Chemistry     Full-text available via subscription   (Followers: 2)
ISRN Environmental Chemistry     Open Access  
JBIC Journal of Biological Inorganic Chemistry     Hybrid Journal   (Followers: 2)
JCP : BioChemical Physics     Hybrid Journal  
JOT Journal für Oberflächentechnik     Hybrid Journal  
JOT-International Surface Technology     Hybrid Journal   (Followers: 1)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 2)
Journal of Chromatography & Separation Techniques     Open Access   (Followers: 7)
Journal of Microbial & Biochemical Technology     Open Access   (Followers: 1)
Journal of Thermodynamics & Catalysis     Open Access   (Followers: 2)
Journal of Adhesion     Hybrid Journal   (Followers: 7)
Journal of Adhesion Science and Technology     Hybrid Journal   (Followers: 6)
Journal of Advanced Oxidation Technologies     Full-text available via subscription   (Followers: 1)
Journal of Advances in Chemistry     Open Access   (Followers: 2)
Journal of Agricultural and Food Chemistry     Full-text available via subscription   (Followers: 15)
Journal of Amino Acids     Open Access   (Followers: 3)
Journal of Analytical Sciences, Methods and Instrumentation     Open Access   (Followers: 1)
Journal of AOAC International     Full-text available via subscription   (Followers: 8)
Journal of Applied Chemistry     Open Access   (Followers: 1)
Journal of Applied Spectroscopy     Hybrid Journal   (Followers: 7)
Journal of Automated Methods and Management in Chemistry     Open Access  
Journal of Biomaterials and Nanobiotechnology     Open Access   (Followers: 4)
Journal of Carbohydrate Chemistry     Hybrid Journal   (Followers: 4)
Journal of Catalysis     Hybrid Journal   (Followers: 6)
Journal of Catalysts     Open Access  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 6)
Journal of Chemical Education     Full-text available via subscription   (Followers: 14)
Journal of Chemical Health Risks     Open Access   (Followers: 2)
Journal of Chemical Information and Modeling     Full-text available via subscription   (Followers: 5)
Journal of Chemical Research     Full-text available via subscription   (Followers: 5)
Journal of Chemical Science and Technology     Open Access   (Followers: 1)
Journal of Chemical Sciences     Partially Free   (Followers: 15)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 9)
Journal of Cheminformatics     Open Access   (Followers: 1)
Journal of Chemistry     Open Access   (Followers: 3)
Journal of Chemometrics     Hybrid Journal   (Followers: 10)
Journal of Chromatography A     Hybrid Journal   (Followers: 45)
Journal of Chromatography Library     Full-text available via subscription   (Followers: 5)
Journal of Colloid and Interface Science     Hybrid Journal   (Followers: 12)
Journal of Computational Chemistry     Hybrid Journal   (Followers: 13)
Journal of Coordination Chemistry     Hybrid Journal   (Followers: 1)
Journal of Dispersion Science and Technology     Hybrid Journal  
Journal of Encapsulation and Adsorption Sciences     Open Access   (Followers: 5)
Journal of Environmental Chemistry and Ecotoxicology     Open Access   (Followers: 2)
Journal of Flow Chemistry     Full-text available via subscription   (Followers: 1)
Journal of Fluorescence     Hybrid Journal   (Followers: 3)
Journal of Fluorine Chemistry     Hybrid Journal   (Followers: 6)
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 5)
Journal of Great Lakes Research     Hybrid Journal   (Followers: 7)
Journal of Heterocyclic Chemistry     Hybrid Journal   (Followers: 5)

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Journal Cover Journal of Theoretical and Computational Chemistry
   Journal TOC RSS feeds Export to Zotero [9 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0219-6336 - ISSN (Online) 1793-6888
     Published by World Scientific Homepage  [114 journals]   [SJR: 0.286]   [H-I: 16]
  • Theoretical studies on the pyrolysis of (Thion)carbonates
    • Authors: Ping Wu et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. MP2/6-31G(d) was employed to investigate the theoretical calculations on the pyrolysis of alkyl methyl (thion)carbonates, where alkyl groups referred to ethyl, isopropyl and t-butyl groups. Nine possible pathways were considered for the pyrolysis of alkyl methyl thioncarbonates, while only seven possible pathways were found to pyrolyze alkyl methyl carbonates. Both of them had three pathways to generate the desired alkene products. Not only thermal elimination pathways were calculated, other possible mechanisms, such as rearrangements and nucleophilic substitutions, were also considered. The progress of the reactions was also investigated by the calculation of Wiberg bond indices at MP2/6-31G(d) level.
      PubDate: Mon, 25 Aug 2014 01:52:08 GMT
       
  • Thermodynamically controlled Diels–Alder reaction of
           12-N-methylcytisine: A DFT study
    • Authors: Sophia S. Borisevich et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. A DFT study was performed for the Diels–Alder traction of 12-N-methylcytisine with a number of dienophiles (in boiling toluene under atmospheric pressure), namely, N-phenylmaleimide, maleic anhydride, 2,4-benzoquinone, tetracyanoethylene and methyl methacrylate. It was shown that 12-N-methylcytisine selectively reacts with these dienophiles, only the reaction with N-phenylmaleimide (NPM) resulting in the formation of thermodynamically stable adducts, which is consistent with experimental data. This selectivity of 12-N-methylcytisine is attributable to the difference between the properties of the listed dienophiles, which is confirmed by the relative reactivity indices calculated within the framework of the frontier molecular orbital (FMO) and hard and soft (Lewis) acids and bases (HSAB) theories, the thermodynamic and activation parameters of the forward and retro-Diels–Alder reactions. According to analysis of the theoretical results, NPM is characterized by high chemical potential, hardness close to that of 12-N-methylcytisine, and commensurable heights of the activation barriers for the forward and reverse Diels–Alder reactions and also forms stable [4+2] adducts.
      PubDate: Mon, 21 Jul 2014 09:23:26 GMT
       
  • Theoretical study of spectroscopic constants and anharmonic force field of
           formaldehyde
    • Authors: Xuejun Wang et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. The equilibrium geometries of formaldehyde are optimized with B3LYP, B3PW91 and MP2 methods employing three basis sets 6-311++G(2d,2p), aug-cc-pVTZ and cc-pVTZ, respectively, which agree well with the corresponding experimental and previous theoretical data. The best optimized geometries are obtained at the theoretical level B3LYP/6-311++G(2d,2p) basis set. Basing on the calculated equilibrium geometries, the spectroscopic constants and anharmonic force field of H2CO are investigated. The results show that DFT method is superior to MP2 method at the calculation of spectroscopic constants and force constants of H2CO. The vibration–rotation interaction constants and fundamental vibrational wave numbers of H2CO are firstly theoretically calculated. The Coriolis coupling constants, cubic force constants and most of quartic force constants are firstly theoretically predicted.
      PubDate: Mon, 21 Jul 2014 09:23:25 GMT
       
  • Quantum chemical study of the equatorial/axial exchange of different
           substituents in nitrogen and phosphorous-containing 6-membered rings: Role
           of charge transfer interactions
    • Authors: M. Hassan Khodabandeh et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. Understanding the nature of equatorial/axial conversion in six-membered rings is important because of involvement of these motifs in some biological systems. In this work we have studied the equatorial/axial exchange of nitrogen and phosphorous bearing six-membered rings with different representative substituents by using quantum chemistry methods. Three possible routes, i.e. heteroatom inversion and two ring flipping modes were considered. The feasibility of equatorial/axial conversion (based on ΔE#) for the substituted piperidine rings with substituents was in the following order; H>CH3 >Cl~OH~F, whereas for the phosphorous bearing six-membered rings it was H~F>OH>Cl~CH3. In the piperidine system hydrogen and methyl substituents preferred the atom inversion route while the other substituents (Cl, F, OH) favored C4 site ring flipping in equatorial/axial conversion. For the phosphorous bearing rings, however, phosphorous retards the atom inversion mechanism and heteroatom site ring flipping is the preferred route for all substituents. We demonstrate that charge transfer effect is one of the key factors that determines the favored route in the presence of various substituents. We show how wave function analysis by natural bond orbital (NBO) method can be used as a straightforward technique to explain the most favored route in the equatorial/axial conversion of substituted 6-membered rings.
      PubDate: Mon, 21 Jul 2014 01:37:29 GMT
       
  • Multi switching behavior of hydrogen passivated silicene as molecular
           junction: A DFT-NEGF approach
    • Authors: Jaber Jahanbin Sardroodi et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. Electron transport properties of pristine silicon-substituted analogue of pyrene, Si16H8, and its carbon-doped analogue, Si14C2H8, between two semi-infinite aluminum nanochain electrodes were investigated by means of density functional theory plus nonequilibrium green's function method. Here, the current-bias (I–Vb) characteristics were studied in the bias potential range of 0.0 up to 2.0 V in 0.1 V steps by imposing three gate voltages including -3.0, 0.0 and +3.0 V. The considerable result of the present study was the observation of multiple negative differential resistance (NDR) regions, suggesting that the studied systems could be used as nano-multi-switch. The I–Vb behavior of the studied systems along with the observation of the NDR's in each considered gate voltage was interpreted by means of transmission spectrum. These interpretations were carried on by the integration of the transmission spectrum in the corresponding bias window. The observed NDR characteristics including the bias range and current amplitude could be changed by the variations in the applied gate voltage. Controlling NDR characteristics of these devices using the variations of the gate voltage is a major advantage for practical purposes.
      PubDate: Wed, 16 Jul 2014 02:25:24 GMT
       
  • Designing nonlinear optical molecule by incorporating the planar
           tetracoordinate unit NAl4- or CAl42- into decaborane B10H14
    • Authors: Fang Ma et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. Molecular Incorporation is an important approach of providing novel compounds with fascinating structures. In this paper, we theoretically described the incorporation of the central planar tetracoordinate molecules NAl4- or CAl42- into borane cluster B10H14. By molecular orbital analysis, a novel four-fold Al–H bonding interaction was found, and it contributes to the molecular incorporation. In addition, we found that the counterion Li+ is critical for the neutral incorporation species, due to its small atomic radii and little positive charge. To measure the nonlinear optical (NLO) response, the static first hyperpolarizabilities (β0) were evaluated at the second-order Møller–Plesset (MP2) level. The β0 values are 1708 a.u and 8682 a.u for [B10H14 ⋯ NAl4]- and [B10H14 ⋯ CAl4]2-, respectively, which indicates that the charge plays a significant role on deciding the value of β0. Moreover, it is different for the change of β0 value brought by counterion Li+. Li+ decreases the β0 value of [B10H14 ⋯ CAl4]2-, while it increases the β0 value of [B10H14 ⋯ NAl4]-, therein, the sandwich-like B10H14–Li–NAl4(I) exhibits considerable β0 value (31,253 a.u.). This reveals that it is possible to explore high-performance NLO materials based on suitable molecular incorporation. Besides, the present study is also expected to enrich the knowledge of the planar tetracoordinate carbon chemistry and boron chemistry.
      PubDate: Mon, 07 Jul 2014 07:26:51 GMT
       
  • Comparative theoretical synthesis of high-energy explosive
           1,4,5,8-tetranitro-1,4,5,8-tetraazadecalin
    • Authors: Ken-Fa Cheng et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. Reaction mechanisms were proposed in this study for the theoretical synthesis of high-energy 1,4,5,8-tetranitro-1,4,5,8-tetraazadecalin (TNAD). Corresponding computations were performed using density functional theory (DFT) and the Hartree Fock (HF) method with the same 6-31G(d,p) base function. Glyoxal and ethylenediamine were used as the raw materials and were placed into respective gaseous and solvated (water or ethanol) environments to proceed the condensation reaction to form the precursor 1,4,5,8-tetraazadecalin, which subsequently underwent four stages of nitro-group substitution to obtain the target TNAD compound. A whole reaction scheme closely related to the experimental processes was successfully constructed, and the corresponding energy barriers were estimated for each elementary reaction. The findings revealed that the overall activation energy by B3LYP/6-31G(d,p) calculation is 2660.4 kJ/mol, which is lower than the 2832.1 kJ/mol calculated by HF/6-31G(d,p) computation. Furthermore, the reaction has a lower overall energy barrier in the solvated environment than in the gaseous system, being 2389.6 kJ/mol in ethanol, 2428.7 kJ/mol in water and 2660.4 kJ/mol in the gaseous phase. The ethanol-solvated system is suggested to be the most suitable medium for the synthesis of TNAD.
      PubDate: Fri, 04 Jul 2014 13:16:14 GMT
       
  • A theoretical study on the stability and intramolecular interaction in
           5-nitrotetrazolates with the DFT and DFT-D methods
    • Authors: Junqing Yang et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. Two new salts 3,5-diazido-1,2,4-triazolium 5-nitrotetrazolate and 1-methyl-3,5-diazido-1,2,4-triazolium 5-nitrotetrazolate were designed based on the structures of experimentally synthesized 3-azido-1,2,4-triazolium 5-nitro-tetrazolate and 1-methyl-3-azido-1,2,4-triazolium 5-nitro-tetrazolate, to explore new promising candidates for energetic materials and to investigate the influences of the substituents (-CH3 and -N3) and solvent (water) on the intramolecular interactions and properties. The intramolecular hydrogen bonding interactions were investigated by the natural bond orbital (NBO) and the quantum theory of atoms in molecules (QTAIM) analyses using the density functional theory (DFT) and the dispersion correction DFT (DFT-D) methods. The low-lying singlet electronic transitions were estimated using the time-dependent DFT. All four examined salts exist as ionic structures in aqueous solution while acid–base molecular complexes form in gas phase. The hydrogen bond energy (EH) obtained with the DFT-D method is larger than that obtained with the DFT method, but the trend is consistent, i.e. -N3 increases while -CH3 decreases EH. In addition, the position of the strongest electronic absorption peak has a little correlation with the number of -N3 and -CH3 groups. 3,5-diazido-1,2,4-triazolium 5-nitrotetrazolate is a valuable energetic salt with the highest nitrogen content, oxygen coefficient and density and the second highest heat of formation and chemical stability.
      PubDate: Thu, 03 Jul 2014 02:44:35 GMT
       
  • Structural evolution and stabilities of negatively charged lead telluride
           clusters
    • Authors: Yonas Mulugeta et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. The equilibrium geometric structures, relative stabilities and electronic properties of negatively charged lead telluride clusters are systematically investigated using density functional theory (DFT). The result offered both vertical and adiabatic detachment energies (VDEs and ADEs) for these clusters, divulging an outline of alternating values in which odd n clusters exhibited higher values than even n clusters. Simulations found the negatively charged lead telluride clusters with even n to be thermodynamically more stable than their immediate odd n neighbors, with a consistent pattern also being found in their HOMO–LUMO (HL) gaps. Analysis of the clusters dissociation energies found at cluster to be the preferred product of the queried fragmentation processes, consistent with our finding that cluster exhibits enhanced stability. Beyond n = 12, this study showed that the negatively charged (PbTe)n clusters in the size range n = 13 - 20, prefer two-dimensional stacking of face-sharing lead telluride cubical units, where lead and tellurium atoms possess a maximum of five-fold coordination. The preference for six-fold coordination, which is observed in the bulk, was not observed at these cluster sizes.
      PubDate: Mon, 30 Jun 2014 10:02:24 GMT
       
  • Tautomeric transformations and reactivity of isoindole and sila-indole: A
           computational study
    • Authors: Reza Ghiasi et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. In this work, the tautomeric transformations and reactivity of isoindole and sila-isoindole molecules has been explored using the B3LYP/6-311G(d,p) level of theory in gas and solution phases. These calculations show that isoindole isomer has more stability rather than 1-h-isoindole. There is identical trend in silated species. The frontier molecular orbitals (FMO) and band gap energy calculations were performed at the B3LYP/6-311G(d,p) level in gas and various solvent. Solvent effects have been analyzed by using the self-consistent reaction field (SCRF) method based on polarizable continuum model (PCM) in chloroform, chlorobenzene, dichloromethane and tetrahydrofurane. Thermodynamic parameters calculated at room temperature have been analyzed. Also, electron affinities were computed. Local reactivity descriptors as Fukui functions () local softness () and electrophilicity indices () analyses are performed to find out the reactive sites within molecule. Density functional theory (DFT) calculations were performed to compute nitrogen-14 nuclear quadrupole resonance (NQR) spectroscopy parameters.
      PubDate: Mon, 23 Jun 2014 02:08:32 GMT
       
  • Performance comparison of Poisson–Boltzmann equation solvers DelPhi
           and PBSA in calculation of electrostatic solvation energies
    • Authors: Anbang Li
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. Many Poisson–Boltzmann equation (PBE) solvers have been developed to calculate electrostatic energy of biomolecules, and each PBE solver has its advantages. In this study two PBE solvers — DelPhi and PBSA module in AMBER — are compared in terms of calculation results, convergence and program-running time by calculating the electrostatic solvation energy for a test set composed of 4 Kirkwood models and another test set of 25 protein structures. The protein structures were pretreated by AMBER and AMBER99SB force field parameters were used in all calculations. It is found that (i) At fine grids, both PBE solvers can produce accurate results on test set 1 and consistent results with each other on test set 2, with differences between each other varying from several to ~10 kcal/mol. (ii) Under convergence criterion "absolute value of relative error is less than or equal to 2% ( RE ≤ 2%)", both PBE solvers need very fine grids to produce convergent results on small and complex Kirkwood models, while grid spacings of ≤ 0.5 Å–0.6 Å are well enough for them to achieve good convergent results on various molecular structures. We recommend users to adopt such grid spacing in using of these PBE solvers so as to get good enough convergent results. (iii) In terms of time consumption, DelPhi appears to be more time-saving than PBSA. In summary, according to our comparison, DelPhi and PBSA are paralleled good PBE solvers. The convergence of PBSA is a little better than DelPhi, while DelPhi exceeds PBSA in running speed.
      PubDate: Mon, 23 Jun 2014 02:08:32 GMT
       
  • Static second hyperpolarizability of Λ shaped alkaline earth metal
           complexes
    • Authors: Kaushik Hatua et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. A number of Λ shaped complexes of alkaline earth metals Be, Mg and Ca with varying terminal groups have been considered for the theoretical study of their second hyperpolarizability. The chosen complexes are found to be sufficiently stable and for a chosen ligand the stability decreases in the order: Be-complex > Ca-complex > Mg-complex. The calculated results of second hyperpolarizability obtained at different DFT functionals for the 6-311++G(d,p) basis set are found to be fairly consistent. The Λ shaped ligands upon complex formation with metals lead to strong enhancement of second hyperpolarizability. The highest magnitude of cubic polarizability has been predicted for the metal complex having > C(C2H5)2 group. For a chosen ligand, the magnitude of second hyperpolarizability increases in the order Be-complex < Mg-complex < Ca-complex which is the order of increasing size and electropositive character of the metal. The variation of second hyperpolarizability among the investigated metal complexes has been explained in terms of the transition energy and transition moment associated with the most intense electronic transition.
      PubDate: Wed, 18 Jun 2014 04:01:11 GMT
       
  • Study on structures and electronic properties of neutral and anionic
           TiSin(0,-1) (n = 1–8) clusters using G4 theory
    • Authors: Jun Lu et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. The geometries, electronic structures and energies of small TiSin species (n = 1–8) and their anions were systematically investigated by G4 theory. The ground-state structures of these clusters are presented herein. For neutral TiSin (n = 1–8), the spin multiplicities of the ground-state structures are singlet, with the exception of n = 2, which exists in a triplet state. For anionic TiSin-, the spin multiplicities of the ground-state structures are doublet, with the exception of n = 2, which is quartet. The adiabatic electron affinities for TiSin are estimated to be 1.31 eV (TiSi), 1.46 eV (TiSi2), 1.53 eV (TiSi3), 1.71 eV (TiSi4), 2.06 eV (TiSi5), 2.16 eV (TiSi6), 2.20 eV (TiSi7) and 2.39 eV (TiSi8). In comparison with the available experimental data, the calculated adiabatic electron affinities differ from experimental values by an average absolute deviation of only 0.03 eV. Additionally, the dissociation energies of Ti atoms from TiSin, and Si atoms from TiSin and Sin clusters are estimated to examine relative stabilities.
      PubDate: Tue, 03 Jun 2014 02:41:28 GMT
       
  • Transition metal Mo-doped boron clusters: A computational investigation
    • Authors: Run-Ning Zhao et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. Geometries associated with relative stabilities and energy gaps of the Mo-doped boron clusters have been investigated systematically by using density functional theory. The critical size of Mo-encapsulated Bn structures emerges as n = 10, the evaluated relative stabilities in term of the calculated fragmentation energies reveal that the MoB6 has enhanced stabilities over their neighboring clusters. Furthermore, the calculated polarities of the MoBn reveal that the hypercoordinated planar MoB10 wheel is a weakened polar molecule and MoB11 ring is a nonpolar molecule, and aromatic properties are discussed. Additionally, the MoB10 cluster with smaller highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap is supposed to be stronger chemical activity and smaller chemical hardness. Moreover, the recorded natural populations show that the charges transfer from boron framework to Mo atom. It should be pointed out that the remarkable charge-transfer features of MoBn clusters are distinctly similar to those of transitional metal (TM)-doped Sin clusters; growth-pattern of the TMBn depends on the doped TM impurity.
      PubDate: Thu, 29 May 2014 00:49:21 GMT
       
  • Study on the cooperativity of hydrogen bonds between H2Y and HX (X = F,
           Cl, Br; Y = O, S, Se)
    • Authors: Hexiu Liu et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. The structure characteristics, interaction energies, cooperative energies of the complexes between chalcogen hydrides (H2Y) and halogen hydrides (HX) have been studied theoretically at the MP2 level with aug-cc-pVTZ basis set in this paper. The conclusions show that there are strong interactions between H2Y and HX. The stability of the complex is decided by the electronegativity of the negatively charged atom. The cooperativity is observed in the two or three hydrogen bonds of each trimer structures in title system. The values of the cooperative energies and the cooperative contributions all illustrate that the cooperativity is of great importance in these complexes. The "atoms in molecules" (AIM) analyses show that the complexes in title system are mainly electrostatic interactions (closed-shell interactions) in character. For H⋯O bonds in H2O⋯HF⋯H2O, H2O⋯HBr⋯H2O and HF⋯H2O⋯HF, the 1 < Vc ∕ Gc < 2 and -Gc < Hc < 0 indicate the interactions in these compounds are between closed-shell interaction and opened-shell interaction.
      PubDate: Thu, 29 May 2014 00:49:11 GMT
       
  • The study on the geometry and electronic properties of (WO3)x/(TiO2)y
           heterostructure by using the layered structural model
    • Authors: Yong-Qiang Zhang et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. The layered structural model was proposed to study the geometry and electronic properties of the (WO3)x/(TiO2)y heterostructures in this paper. The geometry and electronic properties were affected greatly by the relative proportion of TiO2 and WO3 in the nanocomposites. The minimum band gap of (WO3)x/(TiO2)y heterostructures decreased with the proportion of WO3 increasing but increased with the proportion of TiO2 increasing. Interestingly, electrons at the upper valence band (VB) can be directly excited from 2p and 3d orbitals of titania to the conduction band (CB), which was mainly consisted of 5d orbitals of tungsten trioxide. The effective electron mass of (WO3)x/(TiO2)y heterostructures was higher than that of pure TiO2. It indicated that the electron–hole recombination rate of hybrid (WO3)x/(TiO2)y heterostructure was lower than that of pure TiO2, which might imply that photocatalytic activities of the hybrid (WO3)x/(TiO2)y heterostructures were enhanced under visible light irradiation. The theoretical results might offer a new useful guide for designing semiconductors photocatalyst, such as heterostructure nanocomposites.
      PubDate: Wed, 21 May 2014 03:11:37 GMT
       
  • Theoretical studies on the structure and property of alkylated
           dipenylamine antioxidants
    • Authors: Zhongping Tang et al
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. Diarylamines (Ar2NH) are generally used as antioxidants to inhibit or retard the auto-oxidation degradation of lubricating oil by trapping ROO• radicals. In the present study, 20 kinds of 4,4′-disubstituted diphenylamine compounds were investigated through density functional theory (DFT) calculations. The results indicate that the N–H bond dissociation enthalpy (BDE) linearly correlates its one-electron oxidation potential, the difference in Mulliken atomic charge on the two atoms of N–H bond, the reaction rate constant of hydrogen transfer from Ar2NH to peroxy radical, and the chemical hardness of the resulted Ar2N• radical, respectively. The substitution of alkyl groups (electron-donating groups) decreases the N–H BDE, one-electron oxidation potential and the reaction rate constant, while that of significant electron-withdrawing groups such as −NO2 and −COOCH3 increases these three parameters. The electron-donating groups such as alkyls could improve the antioxidation performance of 4,4′-disubstitued diphenylamines whereas electron-withdrawing groups have the contrary effect. In addition, the frontier molecular orbital of Ar2NH has been also analyzed.
      PubDate: Wed, 21 May 2014 03:11:37 GMT
       
 
 
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