The TB-LMTO method and its relation to the screened KKR method

The main formal aspects of the TB-LMTO and the screened KKR method are reviewed in terms of multiple scattering theory (scattered wave method) as based on a general reference medium. In terms of the corresponding Green's functions, a comparison is made between these two approaches listing similarities and differences and advantages and disadvantages. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 165–188, 1997     

Application of the dilution method to micro-analysis

Summary 1.Pregl’s, Dubsky’s, or any other modified microDumas nitrogen apparatus and method can be made use of without a micro-chemical balance; 2. the use of a gasometer between the Kipp generator and the combustion tube standardizes the method and has several advantages; 3. removal and renewal of the acid in the initial Kipp generators may be brought about with the exclusion of air.     

A method to evaluate the Sachs formula

A rule-based method for evaluating the Sachs formula is introduced. For simple molecules, such as linear chains and monocycles, the Sachs formula can be evaluated by directly using the rules. For complex molecular systems, the Sachs formula can be evaluated by first breaking up the molecule into constituent pieces of sufficient simplicity so that data for them are available in the data base and then constructing the molecule from the known data by adding all pieces together, one at a time, via a series of binary rules. The method changes the way of evaluating the Sachs formula from a trial-and-error-type numerical search to a purely algebraic manipulation and thus tremendously reduces the computing times. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65 : 19–36, 1997     

Application of the AMO method to the naphthalene molecule

The alternant molecular orbital (AMO) method was applied to the ground state of naphthalene. Both the single and the many-parameter variants lead to substantial improvement in the energy. Comparison with a limited configurational interaction treatment shows that the AMO method is better in the many-parameter variant.

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Zusammenfassung Die Methode der alternierenden MO (AMO) wurde auf den Grundzustand des Naphthalins angewandt. Beide Varianten der Methode, mit einem sowie mit mehreren Parametern, bringen wesentliche Verbesserung in der Energie. Vergleich mit einer beschrÄnkten Konfigurations-Wechselwirkungs-Methode zeigt, da\ die AMO-Methode besser ist, wenn mehrere Parameter angewandt werden.

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Résumé La méthode des orbitales moléculaires alternantes (AMO) est appliquée a l'état-fondamental du naphthalène. Les variantes a un ou plusieurs parametres de cette methode produisent des améliorations substantielles pour l'énergie. La comparison avec une application de la méthode d'interaction de configurations limitée montre que la méthode AMO est plus efficace dans la variante avec plusieurs parametres.

     

Reply to the comment on the energy variation method

The assertion that the energy variation theorem for excited states follows from the classical minmax principle is further reinforced. The problem of minimizing the manifold energy in the non-orthogonal basis is also solved.     

Application of the AMO method to non-alternant systems

The alternant molecular orbital method (AMO ) is more efficient if the molecular orbitals are chosen in an optimal way. A method is given of how to determine the most effective pairing scheme and how to choose the starting molecular orbitals. Applications to non-alternant systems (fulvene and azulene) show that one can achieve substantial improvement in the energy by determining the best MO's .     

Application of the electromigration method to radiochemical studies

The use of the electromigration method for the separation of mixtures of radioactive substances, for the investigation of various equilibria, e. g. complex formation, and for kinetic studies have been considered.     

A comment to the nudged elastic band method

The minimum energy path (MEP) is an important reaction path concept of theoretical chemistry, and the nudged elastic band (NEB) method with its many facets is a central method to determine the MEP. We demonstrate in this comment that the NEB does not have to lead to a steepest descent pathway (as always assumed). In contrast, as long as it is used without spring forces, it can lead to a gradient extremal. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

A least-squares method applied to the hydrogen molecule

A least-squares approach is proposed to remedy some of the weaknesses of the method of moments. It is shown by an application to the hydrogen molecule that the least-squares procedure yields reliable results in cases where the method of moments fails. The prediction of equilibrium internuclear distances by the least-squares method is also found to be more reliable than the corresponding results obtained by the method of moments.     

Refinements to the diastereoisomer-specific method for the analysis of hexabromocyclododecane

The emergence of hexabromocyclododecane (HBCD) as a bromine-based flame retardant of concern is partly attributable to recent measurements on the environmental occurrence of the individual diastereoisomers (alpha, beta and gamma). These measurements were fuelled by a newly developed liquid chromatography/tandem mass spectrometric (LC/MS/MS)-based analytical method. However, in the course of our recent studies on the environmental fate and behaviour of the diastereoisomers of HBCD, some interesting features of the LC/MS/MS method became apparent. For example, the ion signal of the native ions was found to be dependent on the final extract volume. This was true for both biotic and sediment samples and was found to arise from the suppression of the ion signal due to endogenous material in the extracts that escape clean-up. We have also found differences in the stability of the diastereoisomers in different solvents. If left unaccounted for, both factors can compromise analytical measurement data. By way of a series of controlled experiments conducted at our two laboratories [Department of Fisheries & Oceans Canada (DFO) and Environment Canada (EC)], we illustrate these features and demonstrate that use of newly synthesized labelled HBCD isomers [(13-carbon (13C) and deuterium (d18)] can minimize and often circumvent matrix-related effects.     

Semi-empirical corrections to the mixing coefficients for the diatomics-in-molecules method

The diatomics-in-molecules (DIM) method requires information about the wavefunction (i.e. mixing coefficients) and the energy of various states of diatomic fragments. We show here that, if the diatomic energy is obtained from experiment, then it is also important to correct the mixing coefficients by making use of experimental atomic state energies. This point is illustrated by application to the OH⁺(³Σ^?) state manifold.     

Semi-theoretical approach to the applications of the sum peak method

Although application of the sum peak method to determine the PAC parameter was limited to point source like specimens, a theoretical consideration has been made to examine the possibility of application of the sum peak method to specimens with finite dimension in this work. It has been revealed that the sum peak method can be applied to those specimens in the same manner as to point source like ones. Furthermore, the possibility of application of the sum peak method to determinations of the time differential attenuation factor G₂₂/t/ has been discussed, and its procedure has been proposed.     

A method to accelerate the gelation of disulfide-crosslinked hydrogels

A glutathione-disulfide-ended poly(ethylene glycol)(GSSG-PEG-GSSG) was designed. It is a much more efficient accelerator than glutathione disulfide(GSSG) for the gelation of an 8arm-PEG-SH polymer solution, and the gelation time can be tuned from hours to minutes at the physiological p H and temperature. A mechanism was proposed to explain the different behaviors of the GSSG and GSSG-PEG-GSSG gelation systems. Due to the ever-going thiol-disulfide exchange reaction, the thiol-disulfide hydrogels also showed interesting swelling behavior.     

An iterative method to solve the algebraic eigenvalue problem

An iterative method based on perturbation theory in matrix form is described as a procedure to obtain the eigenvalues and eigenvectors of square matrices. Practical vector notation and elementary schematic algorithm codes are given. The particular programming characteristics of the present computational scheme are based upon eigenvector corrections, obtained through a simple Rayleigh–Schrödinger perturbation theory algorithm. The proposed methodological processes can be used to evaluate the eigensystem of large matrices.     

Applications of the simulated annealing method to intermolecular interactions

The Simulated Annealing method using a quantum mechanical potential energy surface is used to study the interactions of molecules and the formation of clusters. The results obtained for a range of systems are in good agreement with other theoretical calculations and experimental data where available.     

Mild method for the conversion of amides to thioamides

Aqueous ammonium sulfide was found to be an ideal substitute for hydrogen sulfide for the thiolysis of activated amides. High yields of the corresponding thioamides were obtained for a broad range of substrates, using two different procedures that are both operationally simple and inexpensive, as well as amenable to large-scale preparation. Preliminary results indicate that aqueous ammonium sulfide may also replace hydrogen sulfide in the synthesis of thionoesters from amides.