O. Kh. Poleshchuk ¹, N. B. Egorov ², D. V. Akimov ², I. I. Zherin ², N. A. Zhuravlev ²

Affiliations
1 Tomsk State Pedagogical University, ul Kievskaya 60, Tomsk - 634061, RU
2 Tomsk Polytechnic University, Lenina Avenue 30, Tomsk - 634050, RU

Abstract

Background/Objectives: The article is devoted to the dependence of the experimental and calculated frequencies in the IR- and Raman-spectra from the molecular mass of the sulfur isotope. Methods/Statistical Analysis: The calculations of the S₈ molecules containing the different sulfur isotopes were carried out using the GAUSSIAN’03 program package. The geometries were first optimized at the gradient-corrected DFT level using the three-parameter fit of the exchangecorrelation potential suggested by Becke in conjunction with the LYP exchange potential (B3LYP). All electron 6-31G(d), and extended cc-PVTZ basis sets were used. The absence of imaginary vibration frequencies confirmed the stationary character of the structures. Findings: IR spectra and Raman spectra of the polycrystalline isotopes α^-32S, α^-33S and α^-34S were obtained. It was found that experimental frequencies of the vibrational spectra of the isotopes of sulfur decrease in a linear manner with an increasing mass of the isotope. From the experimental correlations, the oscillation frequencies for the isotope α^-36S were determined. The results obtained demonstrate that the quantum-chemical calculations are sensitive to the isotopic shifts in the vibrational spectra of sulfur isotopes and are able to assess changes in their thermodynamic properties. Applications/Improvements: The effect of a sulfur isotope shift on the change of thermodynamic parameters.

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O. Kh. Poleshchuk ¹, N. B. Egorov ², D. V. Akimov ², I. I. Zherin ², N. A. Zhuravlev ²

Affiliations
1 Tomsk State Pedagogical University, Ul. Kievskaya, 60, Tomsk, 634061, RU
2 Tomsk Polytechnic University, Lenina Avenue 30, Tomsk, 634050, RU

Abstract

Background/Objectives: In the present work the theoretical methods B3LYP/SDD, GGA and BP86/TZ2P were used for quantum-chemical calculations of lead chalcogenides. Methods/Statistical Analysis: Calculations were carried out using a hybrid method of a functional of density of B3LYP, with an exchange functional to Becke В3 and a correlation functional Lee, Wang and Parr (LYP). As a basic condition were used the SDD pseudo potential for an atom of lead and the D95 double-dzeta as the basis for other atoms. To estimate the enthalpy of formation the semi-empirical method PM3 was used. Findings: It is shown that there are correlations between the experimental and calculated characteristics of lead sulphide, selenide and telluride. The influence of different isotopes of lead, sulphur, selenium and tellurium on the thermodynamic parameters and the Raman spectra for the lead chalcogenides is shown. Applications/Improvements: The results suggest that the use of the density functional method in various versions with different functional and basic conditions.

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