Theoretical analysis of infrared spectrum of 9,10-anthraquinone molecule

For the molecule of 9,10-anthraquinone, vibration frequencies and intensities have been calculated, and a theoretical spectral curve has been plotted, giving an adequate reflection of experimental manifestations over a broad spectral interval. This study made it possible to obtain a correct system of parameters for a model of the 9,10-anthraquinone molecule. Theoretical analysis has provided a basis for distinguishing vibration frequencies, active in the spectrum, that are characteristic with respect to frequency and intensity.K. A. Timiryazev Agricultural Academy. Scientific-Research Institute of Physical Problems. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 169–178, January–February, 1993.     

On the temperature dependence of the probability of structural interisomer transitions of molecules

The properties of the intersection surface of the potential energy surfaces of structural isomers and kinetic characteristics of the reaction, including the physical meaning of the Arrhenius law parameters, are analyzed in detail. A number of corollaries important for determining the probability of the interisomer transition and the influence of the temperature factor on the probability and the pattern of this structural transformation were formulated. The theoretical model used describes the experimental regularities (Arrhenius law) and allows one to calculate the relevant parameters. The reason for manifestation of this regularity is the superposition of two factors, namely, the exponential dependence of the transition probability on the reciprocal temperature and the linear temperature dependence of the level of energy for which this probability is the highest.     

Accuracy in Calculating the Intensities of the Absorption Bands in IR Spectra by Direct Quantum-Chemical Methods

To obtain information on the accuracy of quantum-chemical computations of the integral intensities of the absorption bands in IR spectra, calculations were performed by the density functional and ab initio methods for a number of polyatomic molecules that include the atoms of halogens, sulfur, phosphorus, etc. The results are compared with quantitative experimental data. A sufficient scatter in the calculated and experimental values has been found, but statistical processing of the results by the bootstrap method has revealed a regular deviation that can be partially compensated for by the coordinate scaling method.     

Dependence of the extraction capacity of neutral bidentate organophosphorus compounds on their structure: a quantum chemical study

Correlations between the extraction capacities and molecular structures of organophosphorus compounds (reagents for extraction of transplutonium elements from spent nuclear fuel) were studied using a quantum chemical approach. The results of calculations are in qualitative agreement with experimental data. The approach proposed can be used for analysis of the extraction properties of all classes of organophosphorus compounds and also for prediction of the most efficient organophosphorus extragents with preset properties. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 609–615, April, 2006.     

A REALIZATION OF CERTAIN MODULES FOR THE <Emphasis Type="Italic">N</Emphasis> = 4 SUPERCONFORMAL ALGEBRA AND THE AFFINE LIE ALGEBRA <Emphasis Type="Italic">A</Emphasis><Stack><Subscript>2</Subscript><Superscript>(1)</Superscript></Stack>

We shall first present an explicit realization of the simple N = 4 superconformal vertex algebra L _c ^N?=?4 with central charge c = ?9. This vertex superalgebra is realized inside of the bcβγ system and contains a subalgebra isomorphic to the simple affine vertex algebra L _A1 \( \left(-\frac{3}{2}{\varLambda}_0\right) \). Then we construct a functor from the category of L _c ^N?=?4 -modules with c = ?9 to the category of modules for the admissible affine vertex algebra L _A1 \( \left(-\frac{3}{2}{\varLambda}_0\right) \). By using this construction we construct a family of weight and logarithmic modules for L _c ^N?=?4 and L _A1 \( \left(-\frac{3}{2}{\varLambda}_0\right) \). We also show that a coset subalgebra L _A1 \( \left(-\frac{3}{2}{\varLambda}_0\right) \) is a logarithmic extension of the W(2; 3)-algebra with c = ?10. We discuss some generalizations of our construction based on the extension of affine vertex algebra L _A1 (kΛ ₀) such that k + 2 = 1/p and p is a positive integer.     

From theory of spectra to standardless analysis of molecular objects

The authors discuss the methodology of quantitative analysis of pure substances and mixtures by optical spectra (IR, Raman, UV, etc.) without using samples of standard composition (standardless molecular spectral analysis). An algorithm of quantitative mixture analysis using the reduction of ideal spectra to real ones and computational algorithms of the determination of component concentrations in a mixture taking into account error distribution is proposed. The applicability of the method is estimated using computational experiments parsed and conclusions about the specific features of its work are drawn.     

Quantum chemical estimation of the overtone contribution to the IR spectra of hydrocarbon halogen derivatives

The problem of a comparison of quantum chemical calculation results with the experimental characteristics of molecules is discussed, and it is noted that the accuracy of quantum computations can be most fully evaluated by a comparison of the theoretical results with the experimental spectra. By means of calculations, the contribution of anharmonism to the theoretical values of absorption band intensities in the IR spectra of 15 fluoro and 36 chloro derivatives of hydrocarbons is estimated. The first and second derivatives of the molecular dipole moment are obtained by ab initio quantum chemical calculations with the use of the 6–31G(1d) basis set and allowance for electron correlations by the second order Möller-Plesset method. The performed calculation well reproduces the positions of maxima and the intensity ratio of fundamental, overtone, and complex absorption bands.