Use of the method of atom-atom potentials to analyze the structure of nitrogen-containing compounds

Conclusions It was shown that the model of atom -atom potentials can be used to determine the structure parameters of nitrogen-containing compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1159–1162, May, 1978.     

A novel high-energy-density lithium-free anode dual-ion battery and in situ revealing the interface structure evolution

Lithium-free anode dual-ion batteries have attracted extensive studies due to their simple configuration, reduced cost, high safety and enhanced energy density. For the first time, a novel Li-free DIB based on a carbon paper anode (Li-free CGDIB) is reported in this paper. Carbon paper anodes usually have limited application in DIBs due to their poor electrochemical performance. Herein, by using a lithium bis(fluorosulfonyl)imide (LiFSI)-containing electrolyte, the battery shows outstanding electrochemical performance with a capacity retention of 96% after 300 cycles at 2C with a stable 98% coulombic efficiency and 89% capacity retention after 500 cycles at 5C with a stable coulombic efficiency of 98.5%. Moreover, the electrochemical properties of the CGDIB were investigated with a variety of in situ characterization techniques, such as in situ EIS, XRD and online differential electrochemical mass spectrometry (OEMS). The multifunctional effect of the LiFSI additive on the electrochemical properties of the Li-free CGDIB was also systematically analyzed, including generating a LiF-rich interfacial film, prohibiting Li dendrite growth effectively and forming a defective structure of graphite layers. This design strategy and fundamental analysis show great potential and lay a theoretical foundation for facilitating the further development of DIBs with high energy density.

A novel lithium-free anode dual-ion battery is fabricated based on a carbon paper anode. In situ EIS, XRD and OEMS demonstrate the multi-functional effects of LiFSI on the performance of the Li-free CGDIB.     

Analytical method for the representation of atoms-in-molecules densities

We present analytic refinements and applications of the deformed atomic densities method [Fernández Rico, J.; López, R.; Ramírez, G. J Chem Phys 1999, 110, 4213-4220]. In this method the molecular electron density is partitioned into atomic contributions, using a minimal deformation criterion for every two-center distributions, and the atomic contributions are expanded in spherical harmonics times radial factors. Recurrence relations are introduced for the partition of the two-center distributions, and the final radial factors are expressed in terms of exponential functions multiplied by polynomials. Algorithms for the practical implementation are developed and tested, showing excellent performances. The usefulness of the present approach is illustrated by examining its ability to describe the deformation of atoms in different molecular environments and the relationship between these atomic densities and some chemical properties of molecules.     

Determination of bifurcation in chemical systems. An experimental method

The systems Mn²⁺-malic acid-H₂SO₄-KBrO₃ and Mn²⁺-citric acid-H₂SO₄-KBr-O₃ have been studied in a stirred tank reactor. Transitions from the oscillatory state to the stationary state can occur by four types of bifurcation. All these types can be distinguished experimentally. The bifurcation diagrams for the systems mentioned have been determined.     

Semiempirical parametric method in the theory of vibronic spectra of polyatomic molecules

A semiempirical parametric method for calculating the vibrational structure of the electronic spectra of polyatomic molecules is developed; the method is based on the adiabatic molecular model and uses a single parametric system for all excited states. Within the model approach, simplified analytical expressions for potential surface variation during molecular excitation are derived; the expressions include the principal terms according to the order of magnitude. The first and second derivatives of Coulomb and resonance one-electron integrals with respect to natural coordinates in a basis set of hybrid atomic orbitals are used as parameters. It is shown that the parameters possess distinct locality, are transferable in molecular series, and may be easily ranked according to absolute values; describing a molecular model requires few most significant parameters. Excitation-induced variations of potential surfaces and absorption spectra of some molecules (butadiene, hexatriene, octatetraene) are calculated using only two parameters, which are the same for all molecules. The results of calculations are in good agreement with the experimental data. Supported by RFFR grant No. 95-03-08808. V.I. Vernadskii Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences. Translated fromZhumal Struckturnoi Khimii, Vol. 37, No. 3, pp. 419–431, May–June, 1996.     

Propagator representation for partial structure character in conjugated systems

A new method for the evaluation of partial structure character (PC) in a conjugated molecule is proposed and used to calculate the PCs of some conjugated molecules. When PC is represented by the propagator technique or the method of second quantization, the physical meaning of different types of PC is clarified.received by the Publisher 20 September 1989     

Treating molecules in arbitrary spin states using the parametric two-electron reduced-density-matrix method

Minimizing the electronic energy with respect to a parameterized two-electron reduced density matrix (2-RDM) is known as a parametric variational 2-RDM method. The parametric 2-RDM method with the M 2-RDM parametrization [D. A. Mazziotti, Phys. Rev. Lett. 101, 253002 (2008)] is extended to treat molecules in arbitrary spin states. Like its singlet counterpart, the M parametric 2-RDM method for arbitrary spin states is derived using approximate N-representability conditions, which allow it to capture more correlation energy than coupled cluster with single and double excitations at a lower computational cost. We present energies, optimized bond lengths, potential energy curves, and occupation numbers for a set of molecules in a variety of spin states using the M and K parametric 2-RDM methods as well as several wavefunction methods. We show that the M parametric 2-RDM method can describe bond breaking of open-shell molecules like triplet B(2) and singlet and triplet OH(+) even in the presence of strong correlation. Finally, the computed 2-RDMs are shown to be nearly N-representable at both equilibrium and non-equilibrium geometries.     

The electronic structure of N-methyl-3pyridone and its representation

Quasi-localized MO's have been constructed for the electron system of the three pyridone isomers.     

Use of the CNDO method for the study of the electronic structure and properties of complexes of the transition metals

Conclusions In our view, the material examined in the present review indicates that, in spite of the appearance of more accurate methods of calculating the electronic structure and the increasing possibilities provided for their realization for fairly complex systems, the applied value of simple semiempirical methods, in particular the CNDO method, is far from exhausted. In the near future, semiempirical calculations will probably provide the chief means of studying the electronic structures of complex molecules, by becoming accessible to an increasing circle of chemists.Leningrad State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 17, No. 3, pp. 549–577, May–June, 1976.     

On the representation of atoms and molecules as self-interacting field with internal structure

The nonlinear Schrödinger equation with Gaussian convolution kernel K₂ induces the group SU₃ with reference to the classification of the multiplet structure of the eigenstates. Such a field can be used to describe some atoms (where the outermost electrons are related tos-orbitals) as a self-interacting, extended particle with an internal structure. In the case of those atoms, where the valence electrons are described byp-orbitals, and almost all molecules the Gaussian kernel K₂ has to be generalized by Hermite polynomials. By that, we can formulate a nonlinear field theory, establishing the spatial symmetry of a system via basis structure functions. Thus the symmetry represents the most essential starting-point for treating molecules as quasi-particles with an internal structure. It will be shown that there is some connection with the concept of chirality functions and the Ginzburg — Landau theory of super-conductivity. The latter theory indicates that we can consider the nonlinear Schrödinger equation and its generalizations as a classical field theory being associated with phase transitions.     

2D representation of protein secondary structure sequences and its applications

In terms of the classification of the protein secondary structures, we propose a 2D representation of protein secondary structure sequences. The representation are used to display, analyze, and compare the secondary structure sequences. Based on this representation, we assign the structural class to the protein, and verify the advantage or disadvantage of the methods of predicted protein second structure.     

A visual representation for RNA secondary structure and its application

The graphical representation of biological sequences is an important subject in the area of genome studies. We propose a novel visual representation for RNA secondary structures. Some symmetric properties and information on the base distribution and compositions can be intuitively reflected by the projection graphs of the points corresponding to the RNA secondary structures. Then our method is applied to compute the similarity of 12 classical samples and 11 real RNA secondary structures. The results indicate that our method can not only effectively analyze the similarity between RNA secondary structures but also show a high consistency with other literatures. Moreover, our method only needs the geometrical center of the characteristic curve of the RNA secondary structure to compute the similarity matrix, which means a low computational complexity. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

A representation of the McClelland method of graph splitting. Stack graphs

McClelland's rules on graph splitting can be represented using the generalized graph notation. Generalized graphs are edge- and vertex-weighted graphs, which are becoming important to chemical problems. By this the McClelland method of graph splitting has a wider range of applications. “Stack graphs” are constructed from identical “base graphs” by connecting corresponding vertices from one base to another. Their eigenvalues are related to the eigenvalues of the base graph. Two- and even three-layered graphs may be used as a simple model for the inter-ring interaction in a cyclophane.     

Finite element method parametric study on scratch behavior of polymers

Parametric studies were performed using finite element analysis (FEA) to learn how material and surface properties of polypropylene (PP) affect scratch behavior. Three-dimensional FEA modeling of scratching on a PP substrate with a spherical-tipped indenter is presented. Three different loading conditions, that is constant scratch depth, constant normal load, and linearly increasing normal load, are adopted for this parametric study. From the FEA findings, it is learned that Poisson's ratio has a negligible effect on scratch performance, whereas raising the coefficient of adhesive friction induces a significantly larger residual scratch depth and tangential force on the scratch tip. Increasing the Young's modulus of a material does not necessarily improve its overall scratch performance. On the other hand, modifying the yield stress of a material has a major impact on scratch resistance as a higher yield stress reduces the residual scratch depth. From this numerical effort, it is concluded that the yield stress and coefficient of adhesive friction are the most critical parameters to influence the scratch performance of a material. Analyses also suggest that the general trend in the parametric effect of the above four parameters on scratch behavior is independent of the applied normal load level. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1435–1447, 2007