Download or read book Ab Initio Calculation of Vibrational Circular Dichroism Spectra Using Accurate Post Self Consistent Field Force Fields Trans 2 3 Dideuteriooxirane written by and published by . This book was released on 1996 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ab initio calculation of harmonic force fields using post-self-consistent (post-SCF) methods has recently increased greatly in efficiency. As a result, accurate post-SCF harmonic force fields are now achievable for experimentally accessible chiral molecules. This in turn, permits for the first time, comparison to experiment of ab initio predictions of vibrational circular dichroism (VCD) spectra based on accurate harmonic force fields. This advance is exploited here in the calculation of the VCD spectrum of trans-2,3-dideuteriooxirane using a large basis set MP2 force field. Excellent accord with recent experimental work is achieved. With the exception of C-H and C-D stretching modes, residual differences between predicted and experimental VCD intensities can be attributed to the incomplete inclusion of correlation in the calculation of atomic axial tensors. jg p3.
Download or read book Reviews in Computational Chemistry Volume 7 written by Kenny B. Lipkowitz and published by John Wiley & Sons. This book was released on 2009-09-22 with total page 441 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the seventh volume in the successful series designed to help the chemistry community keep current with the many new developments in computational techniques. The writing style is refreshingly pedagogical and non-mathematical, allowing students and researchers access to computational methods outside their immediate area of expertise. Each invited author approaches a topic with the aim of helping the reader understand the material, solve problems, and locate key references quickly.
Download or read book Chiroptical Spectroscopy written by Prasad L. Polavarapu and published by CRC Press. This book was released on 2016-10-03 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book details chiroptical spectroscopic methods: electronic circular dichroism (ECD), optical rotatory dispersion (ORD), vibrational circular dichroism (VCD), and vibrational Raman optical activity (VROA). For each technique, the text presents experimental methods for measurements and theoretical methods for analyzing the experimental data. It also includes a set of experiments that can be adopted for undergraduate teaching laboratories. Each chapter is written in an easy-to-follow format for novice readers, with necessary theoretical formalism in appendices for advanced readers.
Download or read book Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields written by and published by . This book was released on 1995 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment. The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg.
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1996 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ab Initio Variational Calculations of Molecular Vibrational Rotational Spectra written by Debra J. Searles and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work had its beginnings in the early 1980s at the University ofWollongong, with significant contributions from Dr. Margret Hamilton, Professors Peter G. Burton and Greg Doherty. The emphasis was to develop computer code to solve the nuclear Schrodinger problem. For bent triatomic molecules the project was fmally realized at the University of Newcastle a decade or so later, with the contribution from Ms. Feng Wan g. Aspects of this work are now taught in the quantum mechanics and electron spectroscopy courses at The University of Newcastle. Even now "complete" ab initio solutions of the time-independent SchrOdinger equation is not commonplace for molecules containing four atoms or more. In fact, when using the Eckart-Watson nuclear Hamiltonian a further restriction needs to be imposed; that is, the molecule is restricted to undergoing small amplitudes of vibration. This Hamiltonian is useful for molecules containing massive nuclei and moreover, has been extremely useful in interpreting the rovibrational spectra of small molecules. Nevertheless, a number of nuclear Hamiltonians that do not embed an equilibrium geometry have become well established and are extremely successful in interpreting rovibrational spectra of floppy molecules. Furthermore, solution algorithms vary greatly from research group to research group and it is still unclear which aspects will survive the next decade. For example, even for a triatomic molecule a general form of a potential function has not yet been uncovered that will generally interpolate with accuracy and precision ab initio discrete surfaces.
Download or read book Ab initio Force Fields Vibrational Circular Dichroism Spectra and Model Calculations for Two Methyl Substituted Oxetans written by Richard Anthony Shaw and published by . This book was released on 1986 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Theoretical Calculation of Vibrational Circular Dichroism Spectra written by and published by . This book was released on 1995 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: We report calculations of the mid-IR unpolarized absorption and circular dichroism spectra of 4-methyl-2-oxetanone, 6,8-dioxabicyclo3.2.1octane and 1,7,7-trimethylbicyclo2.2.1heptan-2-one (camphor) based on harmonic force fields calculated using Density Functional Theory (DFT). A hybrid density functional--Becke3LYP--is used. The basis set is 6-31G. The results are in impressive agreement with experimental spectral calculations using the LSDA and BLYP functionals are much less successful. Our results using Becke3LYP/DFT are compared to the predictions of SCF and MP2 calculations. At the present time, the Becke3LYP/DFT methodology is clearly to be preferred in predicting mid-IR vibrational spectra.
Download or read book AB Initio Calculations of Vibrational Absorption and Vibrational Circular Dichroism written by Roberta Bursi and published by . This book was released on 1991 with total page 565 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Spectroscopy written by Jörg Grunenberg and published by John Wiley & Sons. This book was released on 2011-08-24 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unique in its comprehensive coverage of not only theoretical methods but also applications in computational spectroscopy, this ready reference and handbook compiles the developments made over the last few years, from single molecule studies to the simulation of clusters and the solid state, from organic molecules to complex inorganic systems and from basic research to commercial applications in the area of environment relevance. In so doing, it covers a multitude of apparatus-driven technologies, starting with the common and traditional spectroscopic methods, more recent developments (THz), as well as rather unusual methodologies and systems, such as the prediction of parity violation, rare gas HI complexes or theoretical spectroscopy of the transition state. With its summarized results of so many different disciplines, this timely book will be of interest to newcomers to this hot topic while equally informing experts about developments in neighboring fields.
Download or read book Theoretical Prediction of Vibrational Circular Dichroism Spectra of R Glyceraldehyde R Erythrose and R Threose 2 Development of a Procedure to Scale the Force Constant Matrix Expressed in Terms of Internal Coordinates written by and published by . This book was released on 1993 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: A very important objective of the Detection Directorate at the U.S. Army Edgewood Research, Development and Engineering Center is the remote detection of biological materials in the field. One line of thinking, currently being followed, is the recognition that sugars are distinguishing features of biological materials. In Part I of this study, the theoretical prediction of the vibrational circular dichroism (VCD) of the 3 and 4 carbon sugars R- glyceraldehyde, R-erythrose, and R-threose is considered. The calculational procedure used involves determination of the frequencies corresponding to the normal modes of vibration. Since calculated frequencies at the Hartree-Fock level are typically 10% too high, some form of scaling of the frequencies or the force constant matrix is required for quantitative agreement with experimental measurements. In Part II of this study, a scaling method is described, and three key FORTRAN computer programs are presented. Basically, the force constant matrix in internal coordinates at the 6-31G HF level of calculation is scaled to the calculated 6-31G MP2 level of calculation. The force constant matrix in terms of Cartesian coordinates can be determined from a matrix transformation, originally shown by Pulay, involving the force constant matrix in terms of internal coordinates. The scaling constant for each off-diagonal element of the force constant matrix was determined by using the geometric mean Q sub ij = (Q sub i)(Q sub j))(1/2) of the diagonal scaling constants Q sub i and Q sub j. Vibrational circular dichroism, Scaling of force constant matrix.
Download or read book Systematic Studies of Molecular Vibrational Anharmonicity and Vibration rotation Interaction by Self consistent field Higher Derivative Methods written by and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Inclusion of the anharmonicity normal mode vibrations (i.e., the third and fourth (and higher) derivatives of a molecular Born-Oppenheimer potential energy surface) is necessary in order to theoretically reproduce experimental fundamental vibrational frequencies of a molecule. Although ab initio determinations of harmonic vibrational frequencies may give errors of only a few percent by the inclusion of electron correlation within a large basis set for small molecules, in general, molecular fundamental vibrational frequencies are more often available from high resolution vibration-rotation spectra. Recently developed analytic third derivatives methods for self-consistent-field (SCF) wavefunctions have made it possible to examine with previously unavailable accuracy and computational efficiency the anharmonic force fields of small molecules.
Download or read book Theoretical Prediction of Vibrational Circular Dichroism Spectra written by Daniel Zeroka and published by . This book was released on 1990 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: A molecular species that is chiral possesses a Vibrational Circular Dichroism (VCD) spectrum. This study is the first step toward the development of a library of theoretically predicted VCD spectra. At this time we report the result of theoretical studies on several molecules, the dominant species being sugars with 3 - 6 carbon atoms. The procedure used involves stepwise optimizations using MMADS-, MOPAC-, and Gaussian-type calculations. Optimizations at the 3-21G Gaussian level are completed using the Gaussian 82 or CADPAC version 4.0 programs. Frequencies and rotational strengths are determined based on the method of P.J. Stephens, which is incorporated in the CADPAC version 4.0 program. Calculated optimized structures, frequencies, and rotational strengths will be presented. Where available, comparison will be made to experimental results and other calculations; also, a comparison of results using nonscaled versus scaled force fields will be presented. Keywords: Ethylene oxide; Hydrogen perioxide; Hydrogen persulfide; Molecular orbital theory. (AW).
Download or read book Vibrational Optical Activity written by Laurence A. Nafie and published by John Wiley & Sons. This book was released on 2011-07-12 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique book stands as the only comprehensive introduction to vibrational optical activity (VOA) and is the first single book that serves as a complete reference for this relatively new, but increasingly important area of molecular spectroscopy. Key features: A single-source reference on this topic that introduces, describes the background and foundation of this area of spectroscopy. Serves as a guide on how to use it to carry out applications with relevant problem solving. Depth and breadth of the subject is presented in a logical, complete and progressive fashion. Although intended as an introductory text, this book provides in depth coverage of this topic relevant to both students and professionals by taking the reader from basic theory through to practical and instrumental approaches.
Download or read book Molecular Vibrations written by E. Bright Wilson and published by Courier Corporation. This book was released on 2012-05-11 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pedagogical classic and essential reference focuses on mathematics of detailed vibrational analyses of polyatomic molecules, advancing from application of wave mechanics to potential functions and methods of solving secular determinant.
Download or read book Near Infrared Spectroscopy written by Yukihiro Ozaki and published by Springer Nature. This book was released on 2020-11-13 with total page 593 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides knowledge of the basic theory, spectral analysis methods, chemometrics, instrumentation, and applications of near-infrared (NIR) spectroscopy—not as a handbook but rather as a sourcebook of NIR spectroscopy. Thus, some emphasis is placed on the description of basic knowledge that is important in learning and using NIR spectroscopy. The book also deals with applications for a variety of research fields that are very useful for a wide range of readers from graduate students to scientists and engineers in both academia and industry. For readers who are novices in NIR spectroscopy, this book provides a good introduction, and for those who already are familiar with the field it affords an excellent means of strengthening their knowledge about NIR spectroscopy and keeping abreast of recent developments.
Download or read book VCD Spectroscopy for Organic Chemists written by Philip J. Stephens and published by CRC Press. This book was released on 2012-06-25 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stimulated by the increasing importance of chiral molecules as pharmaceuticals and the need for enantiomerically pure drugs, techniques in chiral chemistry have been expanded and refined, especially in the areas of chromatography, asymmetric synthesis, and spectroscopic methods for chiral molecule structural characterization. In addition to synthet
