4,261 research outputs found
VIBRATIONAL ANHARMONICITY AND SCALING THE QUANTUM MECHANICAL MOLECULAR FORCE FIELD
No full text Yu. N. Panchenko, P. Pulay and F. T\""{o}r\""{o}k, J. Mol. Struct. 34, 283 (1976); V.I. Pupyshev, Yu.N. Panchenko, Ch. W. Bock and G. Pongor, J. Chem. Phys. 94, 1247 (1991); Yu. N. Panchenko, G.R. De Mar\'{e} and V.I. Pupyshev, J. Phys. Chem. 99, 17544 (1995); Yu. N. Panchenko, Moscow Univ. Chem. Bull. 51 (5), 23 (1996). D.M. Dennison, Rev. Mod, Phys. 12, 175 (1940); G.E. Hansen and D.M. Dennison, J. Chem. Phys. 20, 313 (1952).Author Institution: Laboratory of Molecular Spectroscopy, Division of Physical Chemistry, Department of Chemistry, M.V. Lomonosov Moscow State University; Laboratory of Molecular Structure and Quantum Mechanics, Division of Physical Chemistry, Department of Chemistry, M.V. Lomonosov Moscow State University; Chemistry Department, Philadelphia College of Textiles \& ScienceThe interrelationship between the scale factors obtained using Pulay's from the anharmonic and the harmonized vibrational frequencies of a light molecule and its heavy analogue is considered in terms of a Morse potential. The determination of the scale factors from the vibrational frequencies of a light molecule is shown to result in smaller deviations of the calculated and experimental vibrational frequencies of its heavy analogue than those of the reverse procedure. In this context the extent to which Dennison's is satisfied is also discussed
TRANSFERABILITY OF PULAY'S SCALE FACTORS IN THE IVa GROUP OF THE MENDELEYEV PERIODIC SYSTEM
No full text P.C. Hariharan and J.A. Pople, Chem. Phys. Lett. 16, 217 (1972). Yu. N. Pancbenko, P. Pulay and F. T\""{o}r\""{o}k, J. Mol. Structure 34, 283 (1976); V.I. Pupyshev, Yu. N. Panchenko, Ch. W. Bock and G. Pongor, J. Chem. Phys. 94, 1247 (1991); Yu. N. Panchenko, G.R. De Mar\'{e} and V.I. Pupyshev, J. Phys. Chem. 99, 17544 (1995); Yu. N. Panchenko, Moscow Univ. Chem. Bull. 51 (5), 23 (1996).Author Institution: Laboratory of Molecular Spectroscopy, Division of Physical Chemistry, Department of Chemistry, M.V. Lomonosov Moscow State University; Laboratoire de Chimie Physique Mol\'{e}culaire, Facult\'{e} des Sciences, CP 160/09, Universit\'{e} Libre de Bruxelles; Laboratory of Molecular Structure and Quantum Mechanics, Division of Physical Chemistry, Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow 119899, Russian Federation.Ab initio quantum mechanical calculations were performed for structures and force fields of 3,3-dimethylbutene-1, cyclopropene, 1-methylcyclopropene, and 1-trimethylsilyl-, 1,2-bis(trimethylsilyl)-, 1-trimethylgermyl-, 1,2-bis(trimethylgermyl)-, 1-trimethylstannyl-, and 1,2-bis(trimethylstannyl)-3,3-dimethylcyclopropene. Scale factors for correction of the quantum mechanical force fields of cyclopropene, 1-methylcyclopropene, and 3,3-dimethylbutene-1 were determined using Pulay's scaling Only the experimental vibrational frequencies of the light isotopomers of these molecules were used in the scaling procedure. The set of scale factors obtained was transferred to the quantum mechanical force fields of all the other molecules mentioned above. The vibrational problems for these molecules were solved. Complete vibrational analyses were carried out for the whole set of these related compounds. Transferability of scale factors for series of related compounds of cyclopropene with heteroatoms from the IVa group of the Mendeleyev Periodic System of chemical elements was demonstrated
MANIFESTATION OF SECONDARY PERIODICITY IN THE STRUCTURAL AND VIBRATIONAL \\ CHARACTERISTICS OF 3,3-DIMETHYLCYCLOPROPENES DI- AND MONOSUBSTITUTED BY \\ --X (X = C, Si, Ge, Sn, Pb)
No full text% Yu. N. Panchenko, G. R. De Mare, A. V. Abramenkov, and A. de Meijere, Spectrochim. Acta% G. R. De Mare, Yu. N. Panchenko, and A. V. Abramenkov, Spectrochim. ActaAuthor Institution: Div. of Phys. Chem., Dept. of Chem., M. V. Lomo-no-sov; Moscow State University, Moscow 119992, Russian Federation; Universite Libre de Bruxelles, Faculte des Sciences; Service de Chimie Quantique et de Photophysique, CP160/09, 50 av.; F. D. Roosevelt, B1050 Brussels, BelgiumThe regularities of changes in the structural parameters and vibrational wavenumbers have been traced for certain moieties of the title compounds. The optimized geometrical parameters and the force fields of disubstituted \mbox{3,3-dimethylcyclopropenes}} \underline{65A}, 575 (2006).} and monosubstituted 3,3-dimethylcyclopropenes} \underline{67A}, 1094 (2007).} were determined at the HF/3-21G* and DDAll levels, respectively. The choice of these theoretical levels was brought about by peculiarities of GAUSSIAN~03 suite of programs for Sn and Pb atoms. The theoretical vibrational wavenumbers were calculated from the corresponding scaled force fields. The regularities obtained in the form of the zigzag lines are analogous to regularities that are characteristic to the atoms of the 14 (IVA) group of the Mendeleyev Periodic Table. This is known as the secondary periodicity phenomenon
SECONDARY PERIODICITY IN THE STRUCTURAL AND VIBRATIONAL CHARACTERISTICS OF 3,3-DIMETHYLCYCLOPROPENES DI- AND MONOSUBSTITUTED BY --X (X = C, Si, Ge, Sn, Pb)
No full text% Yu.~N.~Panchenko, G.~R.~De Mare, A.~V.~Abramenkov, and A.~de~Meijere, \textit{Spectrochim. Acta% G.~R.~De Mare, Yu.~N.~Panchenko, and A.~V.~Abramenkov, \textit{Spectrochim. ActaAuthor Institution: Div. of Phys. Chem., Dept. of Chem., M. V. Lomo\-no\-sov; Moscow State University, Moscow 119992, Russian Federation; Universite Libre de Bruxelles, Faculte des Sciences; Service de Chimie Quantique et de Photophysique, CP160/09, 50 av.; F. D. Roosevelt, B1050 Brussels, BelgiumThe regularities of changes in the structural parameters and vibrational wavenumbers have been traced for certain moieties of the title compounds. The optimized geometrical parameters and the force fields of disubstituted \mbox{3,3-dimethylcyclopropenes} \underline{65A}, 575 (2006).} and monosubstituted 3,3-dimethylcyclopropenes \underline{67A}, 1094 (2007).} were determined at the HF/3-21G* and DDAll levels, respectively. The choice of these theoretical levels was brought about by peculiarities of GAUSSIAN~03 suite of programs for Sn and Pb atoms. The theoretical vibrational wavenumbers were calculated from the corresponding scaled force fields. The regularities obtained in the form of the zigzag lines are analogous to regularities that are characteristic to the atoms of the 14 (IVA) group of the Mendeleyev Periodic Table. This is known as the secondary periodicity phenomenon
METHODS OF SCALING QUANTUM MECHANICAL MOLECULAR FORCE FIELDS
No full textA.G. Yagola, I.V. Kochikov, G.M. Kuramshina and Yu. A. Pentin. ``Inverse Problems of Vibrational Spectroscopy"". VSP, Utrecht. The Netherlands, 1999, Chapter 11, p. 259. Yu, N. Panchenko, J. Mol. Street. 410-411. 327 (1997).Author Institution: Laboratory of Molecular Spectroscopy, Division of Physical Chemistry, Department of Chemistry, M.V. Lomonosov Moscow State UniversityA comparative analysis of various methods of empirical scaling of the quantum mechanical harmonic molecular force fields has been performed. The Pulay method of scaling is stressed to be applicable most successfully in the case where the quantum mechanical force field is determined close to the Hartree-Fock limit. This makes it possible to carry out correction of this force field with maximal retention of the peculiarities inherent in the the molecule under investigation. The solution of the inverse vibrational problem using quantum mechanical force field as a starting one may be considered to be the limiting case of scaling with maximum number of scale factors. Such approach corresponds to the traditional philosophy that searching force field should be closest to the starting . On the contrary, the main physical criterion used in the Pulay scaling procedure is closeness of the vibrational modes determined from the scaled force field to the vibrational modes obtained from the starting quantum mechanical force
TRANSFERABILITY OF SCALE FACTORS VERSUS TRANSFERABILITY OF FORCE CONSTANTS
No full textA.G. Yagola, I.V. Kochikov, G.M. Kuramshina and Yu. A. Pentin. ``Inverse Problems of Vibrational Spectroscopy"". VSP, Utrecht, The Netherlands, 1999. Chapter 11, p. 259. Yu, N. Panchenko, J. Struct. Chem. 40, 548 (1999) (Russian pagination).Author Institution: Laboratory of Molecular Spectroscopy, Division of Physical Chemistry, Department of Chemistry, M.V. Lomonosov Moscow State UniversityIn the techniques for solving the inverse vibrational problem on the basis of quantum-mechanical force fields, it is assumed that the force constants are the same for quasi-equivalent coordinates in similar structural moieties of related . Clearly, this approach ignores characteristics of the force field of each particular molecule. Indeed, this concept implies that all responsibility for possible shifts of frequencies and other spectral features of related molecules (to which the force constants are transferred) lies with changes in the inverse kinetic energy matrix. With scaling of quantum-mechanical force fields, the relative errors indroduced during quantum-mechanical calculations of force constants at a certain theoretical level are assumed to be approximately the same for quasi-equivalent coordinates in similar structural fragments of related molecules. This assumption imposes less stringent constraints than the assumption of trasferability of force constants in series of related
Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, and trimethylstannyl derivatives of 3,3-dimethylcyclopropene. VII. 3,3-Dimethyl-1-(trimethylstannyl) cyclopropene
No full textThe quantum mechanical force fields (QMFF's) of 3,3-dimethyl-1-(tert-butyl)cyclopropene (I), 3,3-dimethyl-1-(trimethylsilyl)cyclopropene (II), 3,3-dimethyl-1-(trimethylgermyl)cyclopropene (III), and 3,3-dimethyl-1-(trimethylstannyl)cyclopropene (IV) were calculated at the HF/3-21G*//HF/3-21G* level. The set of scale factors for the correction of HF/3-21G*//HF/3-21G* QMFF of II was determined using its well-characterised vibrational spectrum. Transferral of the set of scale factors obtained for II to the QMFF's of I, III and IV and calculation of the fundamental frequencies resulted in good agreement between the calculated and previously assigned experimental frequencies of III. This again demonstrates the feasibility of transferral of a set of scale factors obtained for the correction of the QMFF of a molecule to others containing heteroatoms from the same column of the Mendeleyev Periodic Table. Thus the calculations performed permitted the accurate assignment of the fundamental vibrational frequencies in the experimental IR spectrum of IV. The vibrational frequencies of 3,3-dimethyl-1-(tert-butyl)cyclopropene (I) were also calculated from the HF/6-31G*//HF/6-31G* QMFF, scaled by the set of scale factors used previously for the HF/6-31G*//HF/6-31G* QMFF's of II and III. Regularities in the trends of some vibrational frequencies with increasing atomic number of the heteroatom are observed. © 2005 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
REGULARITIES IN VIBRATIONAL SPECTRA OF 1-TERT-BUTYL AND 1,2-DI-TERT-BUTYL DERIVATIVES OF 3,3-DIMETHYLCYCLOPROPENE AND THEIR SILICON, GERMANIUM, AND TIN ANALOGUES
No full text{Yu. N. Panchenko, G. R. De Mare, A. V. Abramenkov, M. S. Baird, V. V. Tverezovsky, A. V. Nizovtsev, and I. G. Bolesov, \textit{Spectrochim. Acta{G. R. De Mare, Yu. N. Panchenko, A. V. Abramenkov, M. S. Baird, V. V. Tverezovsky, A. V. Nizovtsev, and I. G. Bolesov, \textit{Spectrochim. ActaAuthor Institution: Laboratory of Molecular Spectroscopy, Division of Physical Chemistry,; Department of Chemistry, M. V. Lomonosov Moscow State University,; Moscow 119899, Russian Federation; Service de Chimie Quantique et de Photophysique; (Atomes, Molecules et Atmospheres), Faculte des Sciences; CP160/09, Universite Libre de Bruxelles,; Av. F. D. Roosevelt 50, B1050, Brussels, Belgium; Laboratory of Molecular Structure and Quantum Mechanics,; Division of Physical Chemistry, Department of Chemistry,; M. V. Lomonosov Moscow State University,; Moscow 119899, Russian FederationThe changes in the vibrational frequencies of 1-\textit{tert}-butyl and 1,2-di-\textit{tert}-butyl derivatives of 3,3-dimethylcyclopropene which occur when the central carbon atoms of the \textit{tert}-butyl moieties are substituted by silicon, germanium, or tin atoms are examined. The major decrease in the vibrational frequencies concerned (first of all the frequencies of moieties implicating the hetero atoms) is noted for the substitution of the C atom by the Si atom. Indeed, the shifts of these vibrational frequencies on going from the silicon analogue to the germanium one and from the germanium analogue to the tin one are not as pronounced as those for the CSi transition.% }, \underline{\textbf{59A}}, 1733 (2003) (and references therein).}% }, \underline{\textbf{60A}}, 519 (2003) (and references therein).} An explanation is given for such characteristic changes in these vibrational frequencies for the transitions CSiGeSn. The formation of cluster regions in the vibrational spectra is shown for the frequencies of the stretching vibrations of the SnC moieties. It is concluded that the vibrational frequencies corresponding to moieties containing the hetero-atoms tend towards lower limiting values as the mass of the isovalent atoms is increased
Saratov’s plot in Yu. N. Chumakov’s letters
No full textThe article discusses the place of Saratov-based plot in Yu. N. Chumakov’s letters addressed to the author of the article. The subject of discussion in the correspondence is the defense of Yu. N. Chumakov’s dissertation at Saratov University in 1970 and its role in his scientifi c biography. The defense of the dissertation with Yu. M. Lotman as the fi rst opponent became the key event of the Saratov plot and its climax. Having singled out fragments from the correspondence related to the plot of Saratov, the author seeks to explain the direction of the ensuing epistolary dialogue, why the defense of the dissertation was perceived by Yu. N. Chumakov as a more than signifi cant event for him, especially in the context of his dramatic biography. The author proves that the defense was an explosion of the linear sequence of the text of life, which dramatically changed the fate of the scientist. The desire to talk in detail about the defense, to fi nd out what impression it made, and to look at what was happening on that memorable day for him through the eyes of the addressee of the letter, betrayed the desire to read and interpret his fate again and again. Particular attention is paid in the correspondence to the personalities of such outstanding philologists, professors of Saratov University as A. P. Skaftymov and E. I. Pokusaev. Yu. N. Chumakov was not A. P. Skaftymov’s student and was not familiar with him, but specifi cally noted the acquisition and subsequent development of the principles of a scientifi c approach to the work, set out in his theoretical article in 1923. About the personality of E. I. Pokusaev, his supervisor, and the history of the relationship with him, Yu. N. Chumakov wrote in great detail. Having told about the role of E. I. Pokusaev, who supported the dissertation at the defense, and having outlined his complex, large and humanly attractive personality, Yu.N. Chumakov completes the plot of Saratov, which was very meaningful for him, primarily for self-understanding of his scientifi c path
Yu. N. Chumakov: Memories of Meeting Yu. M. Lotman
No full textThe article features an excerpt from Chumakov’s memoirs, describing how, in the late 1960s, he got acquainted with Lotman’s book Lectures on Structural Poetics and then met the author of the lectures at the Pushkin Conference in Pskov. According to the memoirist, Lotman’s Lectures on Structural Poetics gave literary studies in the 1970s a new language, which may then have been modified within some other schools of literary studies, but it laid the foundation for the scientific description of the fiction text. Investigation of the fiction text has been characterized since the late 1960s by the structuralist approach. The memoirs also mention Chumakov’s defending his candidate dissertation, in which Lotman acted as an opponent (the dissertation was entitled “Problems of Pushkin’s Poetics: (Lyrics, The Stone Guest, Eugene Onegin)” and was defended in Saratov, in 1970.
One part of Chumakov’s candidate dissertation, as well as his report at the Pushkin conference in Pskov, was devoted to the role of the notes and “Passages from Onegin’s Journey” in Pushkin’s novel “Eugene Onegin”. Independently of each other, Chumakov and Lotman came to the conclusion that the notes are not a supplement, but real independent parts within the novel in verse, along with its eight chapters
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