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  Subjects -> CHEMISTRY (Total: 767 journals)
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CHEMISTRY (531 journals)            First | 1 2 3 4 5 6 | Last

Glycobiology Insights     Open Access   (Followers: 1)
Graphene     Open Access   (Followers: 9)
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: 18)
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: 10)
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: 4)
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: 1)
International Journal of Medicinal Chemistry     Open Access   (Followers: 7)
International Journal of Minerals, Metallurgy, and Materials     Hybrid Journal   (Followers: 6)
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: 5)
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: 3)
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  
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: 3)
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: 13)
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: 13)
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: 44)
Journal of Chromatography Library     Full-text available via subscription   (Followers: 5)
Journal of Colloid and Interface Science     Hybrid Journal   (Followers: 11)
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)

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Journal Cover Journal of Theoretical and Computational Chemistry
   [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]
  • 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
       
  • 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
       
  • Kinetic model for the large deformation of cylindrical gels
    • Authors: Xiaomei Yao et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 13, Issue 04, June 2014. Here we investigate the kinetic model for the large deformation theory of hydrogel under the outside stimulations. We present the large deformation dynamical model in the following two points. (1) The phase transition caused by the deformation gradient is concerned, which makes the model more integral. (2) Based on the steady-state model, the time-dependent large deformation model is proposed and the time developing process is investigated. Considering the force of the large deformation, we introduce the heat equation to express the transformation of the chemical potential. The extended model can be used to describe the development of the large deformation. We present numerical examples of the cylindrical hydrogel for one- and two-dimensional cases under pressure and stretch. Besides, some key parameters are studied to test the model. Firstly the dry gel swells freely to form hydrogel in the solvent and acts in different stimulation. Here we investigate the relation of strain-stress by theoretical model and numerical computation. The result is completely consistent with the chemical experiments.
      PubDate: Tue, 01 Jul 2014 10:21:07 GMT
       
  • Theoretical study on supramolecular chemistry of alkali-metal cations with
           crown ether derivatized thiophenes
    • Authors: Qin Wang et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 13, Issue 04, June 2014. This paper describes systemically a theoretical research on the interaction of alkali-metal cations (Li+, Na+, K+ and Rb+) with five different crown ether derivatized thiophenes using density functional theory (DFT). The fully optimized geometries have been performed with real frequencies which indicate the minima states. The optimized structures and electronic properties, such as HOMO and LUMO energies, bandgaps of the free ligands L (L1-L5), the complexes L/M+ (Li+, Na+, K+ and Rb+) have been performed at B3LYP/6-31+G(d,p) and Lanl2DZ level. Natural bond orbital (NBO) and frequency analysis are discussed on the basis of the optimized geometric structures. The main driving forces of the coordination in host–guest molecules are investigated, the electron-donating O offers lone pair electrons to the contacting LP* (1-center valence antibond lone pair) of alkali-metal cations. In addition, the transition energies are calculated by the time-dependent density functional theory (TD-DFT). A theoretical research on the interaction of alkali-metal cations (Li+, Na+, K+ and Rb+) with five different crown ether derivatized thiophenes using density functional theory. The optimized structures and electronic properties, such as HOMO and LUMO energies, band gaps of the free ligands L (L1-L5), the complexes L/M+ (Li+, Na+, K+ and Rb+) have been performed at B3LYP/6-31+G(d,p) and Lanl2DZ level, and the transition energies are calculated by the time-dependent density functional theory.
      PubDate: Tue, 01 Jul 2014 10:21:02 GMT
       
  • Probing the structure and aromaticity in coinage Rhenium trimer and its
           all-metal compounds Re3Li2+, Re3X3+ (X = Be, Mg and Ca) and Re3Y (Y = Al
           and Ga)
    • Authors: Qiao Jin et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 13, Issue 04, June 2014. The extensive search for the global minimum structure of at the B3LYP/LANL2DZ level of the theory revealed that is the ground state. Molecular orbital (MO) analysis reveal that delocalized partial σ and δ bonding in makes partial (σ- and δ-) aromaticity. The multiple d-orbital aromaticities are responsible for a three-center metal–metal bond of the triangular Re3. We also search the pyramidal Re3Li2+, Re3X3+ (X = Be, Mg and Ca) and Re3Y (Y = Al and Ga) clusters containing to reveal that the was preserved perfectly in all-metal compounds, which also possess partially σ- and δ-multiple aromatic characters. • We studied the Re+3, Re3Li2+, Re3X3+ (X = Be, Mg, and Ca), and Re3Y (Y = Al and Ga) clusters. • The trimer Re+3 (D3h, 5A1) exhibits the partially σ- and δ- multiple aromaticity. • The Re3Y (C3v, 3A1) (Y = Al and Ga) complexes possess ϕ-aromaticity.
      PubDate: Tue, 01 Jul 2014 10:20:52 GMT
       
  • Free energy profiles of ion permeation and doxorubicin translocation in
           TolC
    • Authors: Beibei Wang et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 13, Issue 04, June 2014. The outer membrane protein TolC of Escherichia coli forms a channel-tunnel pore spanning the periplasmic space and outer membrane, serving as the main exit duct for bacteria multidrug resistance and protein export. Many aspects of the transport mechanism of TolC are still unclear. Here, we have investigated the substrate permeability and gating mechanism of TolC by calculating the potential of mean forces (PMFs) for transporting sodium ion and doxorubicin through TolC using the adaptive biasing force (ABF) method. The transport mechanism is turned out to be substrate dependent. It is found that the periplasmic gate is required to open for the passage of both Na+ and doxorubicin, but the conformational gating does not lead to permeation barrier for Na+ at this region. The extracellular loops and K283 residues cause permeation barriers for Na+ at the extracellular entrance, but not for doxorubicin due to the extensive interactions between the drug molecule and the protein. TolC exhibits high conformational flexibility during the transport of Na+, while doxorubicin seems to be able to stabilize TolC in the resting state with the periplasmic gate closed. The association of the TolC docking domain of AcrB does not lower the permeation barrier for doxorubicin at the periplasmic gate, while the gate opening induces the dissociation of the TolC–AcrB complex. • The potential of mean forces for transporting sodium ion and doxorubicin through the outer membrane protein TolC are obtained. • The permeation barrier for Na+ locates at the extracellular side, while the barrier for doxorubicin is at the periplasmic side. • The association with the inner membrane transporter AcrB is unable to lower the barrier of doxorubicin translocation.
      PubDate: Tue, 01 Jul 2014 10:20:47 GMT
       
  • Tests of second-generation and third-generation density functionals for
           electron affinities of the alkylthio radicals
    • Authors: Aifang Gao et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 13, Issue 04, June 2014. The molecular structures and electron affinities of the R–S/R–S-(R=CH3, C2H5, n-C3H7, n-C4H9, n-C5H11, i-C3H7, i-C4H9, t-C4H9) species have been studied using 17 pure and hybrid density functionals (five generalized gradient approximation (GGA) methods, six hybrid GGAs, one meta GGA method and five hybrid meta GGAs). The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted by DZP++. The geometries are fully optimized with each DFT method and discussed. Harmonic vibrational frequencies are found to be within 3.5% of available experimental values for most functionals. Three different types of the neutral-anion energy separations have been presented. The theoretical electron affinities of alkylthio radicals are in good agreement with the experiment data. The M06 method is very good for the adiabatic electron affinity calculations, and the average absolute error is 0.0439 eV. The HCTH method performs better for EA prediction. The M06-HF, mPWPW91, VSXC and B98 are also reasonable. The most reliable adiabatic electron affinities are predicted to be 1.864 eV (CH3S), 1.946 eV (C2H5S), 1.959 eV (n-C3H7S), 1.970 eV (n-C4H9S), 1.982 eV (n-C5H11S), 2.053 eV (i-C3H7S), 1.991 eV (i-C4H9S) and 2.100 eV (t-C4H9S) at the M06/DZP++ level of theory, respectively. • The alkylthio radicals' geometries are optimized with 17 DFT methods and discussed. • Three different types of the neutral-anion energy separations and harmonic vibrational frequencies are reported. • The M06 method is the most reliable method for predicting the electron affinities.
      PubDate: Tue, 01 Jul 2014 10:20:43 GMT
       
  • Molecular simulation of ibuprofen passing across POPC membrane
    • Authors: Wei Liu et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 13, Issue 04, June 2014. Permeability assessment is an important procedure in the drug development process, and drug partitioning in membrane bilayer is related to permeability. To investigate the pH dependence on drug partitioning, the process of different ionization state of ibuprofen passing across POPC bilayer was studied using molecular dynamics simulation. The results show that both atomic charge scheme and ionization state of the drug affect the value and shape of energy profile when passing across the POPC bilayer. The neutral ibuprofen (ibuprofen under acidic condition) has a much lower energy barrier as compared with the anionic ibuprofen (ibuprofen under basic condition). Meantime, hydrogen bond analysis also certifies that it is easy for neutral ibuprofen to pass from bulk water to bilayer center. Our calculation suggests that the ionization state of ibuprofen may be changed between neutral and anionic state when passing across membrane: it may be ionized outside the membrane and neutralized inside the membrane. The transmembrane process of ibuprofen with different ionization states was studied using molecular dynamics simulation. The results show that neutral ibuprofen has a much lower energy barrier as compared with the anionic ibuprofen. The ionization state of ibuprofen may be changed between neutral and anionic state as passing across membrane.
      PubDate: Tue, 01 Jul 2014 10:20:36 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
       
  • A density functional theory study of the hydration of calcium ions
           confined in the interlayer space of montmorillonites
    • Authors: sales@wspc.com.sg (Zhaoyang Lou)
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. The structures of Ca2+ hydrates in the interlayer space of montmorillonites (MMT) were studied by periodic density functional theory (DFT) calculations under the GGA/PBE approximation. Affected by the internal surfaces, which are rich of negative charge, the Ca2+ hydration exhibits different behaviors from that in gas phase. The Ca2+ is located at the six-oxygen-ring (SOR) on the internal surface in dry MMT, while the incoming water molecules bind with the Ca2+, the O atoms on surface, and/or with each other. The water molecules have a tendency of forming a hydrogen bond (HB) network that connects the upper and lower surfaces. Attracted by surrounding water molecules, the Ca2+ gradually moves outward with increasing number of water molecules. Moreover, the hydration energy (EH) of Ca2+ is determined not only by the interaction between Ca2+ and H2O, but also by that among Ca2+, H2O and the surfaces. As a result, the EH has only small changes for additional incoming water molecules, in contrast to the great and monotonic decrease in gas phase.
      PubDate: Mon, 28 Apr 2014 03:58:29 GMT
       
  • Structural stabilities and transformations in cationized asparagine at
           finite temperatures: An ab initio molecular dynamics study
    • Authors: Shoutian Sun et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 0, Issue 0, Ahead of Print. The cationic complexes of Asparagine (Asn), M+(Asn), with M+ = Li+, Na+, K+, Cs+, and H+, are models for studying the interaction between cations and Asn. Ab initio molecular dynamics (AIMD) method is employed to simulate their behavior at finite temperatures. Structural transformation between conformers is observed, which becomes progressively easier as the cation varies from Li+, to Na+, K+, Cs+, and H+. The fluctuation of the M+–N and M+–O distances and rotation of torsional angles are significant even at room temperature for K+, Cs+ and H+. Vibrational profiles based on AIMD trajectories provide insights into the broadening and shifts in relative intensities observed in the vibrational spectra measured by infrared multi-photon dissociation (IRMPD) experiments.
      PubDate: Fri, 21 Mar 2014 09:11:46 GMT
       
  • Folding simulation of Trp-cage utilizing a new AMBER compatible force
           field with coupled main chain torsions
    • Authors: Lirong Mou et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 0, Issue 0, Ahead of Print. A newly developed AMBER compatible force field with coupled backbone torsion potential terms (AMBER032D) is utilized in a folding simulation of a mini-protein Trp-cage. Through replica exchange and direct molecular dynamics (MD) simulations, a multi-step folding mechanism with a synergetic folding of the hydrophobic core (HPC) and the α-helix in the final stage is suggested. The native structure has the lowest free energy and the melting temperature predicted from the specific heat capacity Cv is only 12 K higher than the experimental measurement. This study, together with our previous study, shows that AMBER032D is an accurate force field that can be used for protein folding simulations.
      PubDate: Fri, 21 Mar 2014 09:11:46 GMT
       
  • Theoretical investigations of structures and properties of Au and S
           substituted poly (2,3-di-(4′-hydroxyphenyl)-1,4-phenylene ethynyl)
           at different electric field intensities
    • Authors: sales@wspc.com.sg (Jian Zhang)
      Abstract: Journal of Theoretical and Computational Chemistry, Ahead of Print. Theoretical investigations on Au and S substituted poly (2,3-di-(4′-hydroxyphenyl)-1,4-phenylene ethynyl) as a molecular wire have been carried out by incorporating the external electric field (EF). The results demonstrate that both geometric and electronic structures of conjugated molecular wire are sensitive to EF. The Z component of the dipole moment and total dipole moment increases continuously since EF polarizes the molecule. Static EF modifies the frontline molecular orbitals and HLG. The I-V curve indicates the symmetrical trend respect to the original point.
      PubDate: Fri, 21 Mar 2014 09:11:45 GMT
       
  • A density functional approach toward structural features and properties of
           C20…N2X2 (X = H, F, Cl, Br, Me) molecules
    • Authors: Reza Ghiasi et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 0, Issue 0, Ahead of Print. In this work, the interaction of C20 with N2X2 (X = H, F, Cl, Br, Me) molecules has been explored using the B3LYP, M062x methods and 6-311G(d,p) and 6-311+G(d,p) basis sets. The interaction energies (IEs) obtained with standard method were corrected by basis set superposition error (BSSE) during the geometry optimization for all molecules at the same levels of theory. It was found C20…N2H2 interaction is stronger than the interaction of other N2X2 (X = F, Cl, Br, Me) with C20. Highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO, respectively) levels are illustrated by density of states spectra (DOS). The nucleus-independent chemical shifts (NICSs) confirm that C20…N2X2 molecules exhibit aromatic characteristics. Geometries obtained from DFT calculations were used to perform NBO analysis. Also, 14N NQR parameters of the C20…N2X2 molecules are predicted.
      PubDate: Fri, 21 Mar 2014 09:11:44 GMT
       
  • Theoretical study on the formation of carbon disulfide and ammonia from
           thermal decomposition products of thiourea
    • Authors: Zerong Daniel Wang et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 0, Issue 0, Ahead of Print. The formation of carbon disulfide (CS2) and ammonia (NH3) from the thermal decomposition products of thiourea has been studied with MP2, and hybrid module-based density functional theory methods (B3LYP, MPW1PW91 and PBE1PBE), each in conjunction with five different basis sets (6-31+G(2d,2p), 6-311++G(2d,2p), DGDZVP, DGDZVP2 and DGTZVP). The free energy changes and activation energies for all the five primitive reactions involved in the formation of CS2 and NH3 have been compared and discussed. The results indicate that CS2 is most likely formed in a consecutive reaction path that consists of the addition of hydrogen sulfide (H2S) to isothiocyanic acid (HNCS) to generate carbamodithioic acid and subsequent decomposition of carbamodithioic acid. By contrast, thiocyanic acid (HSCN) as the structural isomer of isothiocyanic acid is not likely the source of CS2.
      PubDate: Tue, 18 Mar 2014 08:27:01 GMT
       
  • First principles study on energetic, structural, and electronic properties
           of defective g-C3N4-zz3 nanotubes
    • Authors: Seifollah Jalili et al
      Abstract: Journal of Theoretical and Computational Chemistry, Volume 0, Issue 0, Ahead of Print. The energetic, electronic and structural properties of defective g-C3N4-zz3 nanotubes are considered based on spin-polarized density-functional theory calculations. Nine basic system types with vacancy defects are characterized by their stabilization energies and band gaps. It is found that the nitrogen atom denoted as N3 is the most favorable atom for a vacancy defect. In all cases, local bond reconstruction occurs in the presence of vacancy defects. The role of C/N bond rotations on the above properties has been also investigated. The results show that N1–C3 bond rotation is the most favorable rotational defect. In addition, the electronic properties of the semiconducting g-C3N4-zz3 nanotube with defects have been studied using band structure and density of states plots.
      PubDate: Thu, 06 Mar 2014 12:41:23 GMT
       
 
 
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