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Book Ab Initio Variational Calculations of Molecular Vibrational Rotational Spectra

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.

Book Vibrational rotational Spectroscopy And Molecular Dynamics

Download or read book Vibrational rotational Spectroscopy And Molecular Dynamics written by Dusan Papousek and published by World Scientific. This book was released on 1997-10-31 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book reviews the results of vibration-rotational spectroscopy of molecules obtained recently by combining modern computational methods of quantum chemistry with the new techniques of high-resolution rotational and vibration-rotational spectroscopy. It shows for example that the tunneling vibration-rotational spectroscopy of the van der Waals complexes provides a new look at intermolecular forces while the high precision and sensitivity of the submillimeter-wave and Fourier transform microwave spectroscopy make it possible to study complex rotational spectra of molecules in excited vibrational states. New results of high level ab initio quantum chemical computations of vibrational and rotational energy levels and dipole moment functions of unusual molecules will be discussed together with the recent discovery of clustering of energy levels in asymmetric tops. Group theoretical analysis of floppy molecules, especially the tunneling effects in nonrigid molecules, will also be discussed.

Book Inverse Problems of Vibrational Spectroscopy

Download or read book Inverse Problems of Vibrational Spectroscopy written by A. G. Yagola and published by Walter de Gruyter GmbH & Co KG. This book was released on 2014-10-16 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Inverse and Ill-Posed Problems Series is a series of monographs publishing postgraduate level information on inverse and ill-posed problems for an international readership of professional scientists and researchers. The series aims to publish works which involve both theory and applications in, e.g., physics, medicine, geophysics, acoustics, electrodynamics, tomography, and ecology.

Book Coupled Cluster Predictions of the Rotational and Vibrational Spectra of Molecular Ions

Download or read book Coupled Cluster Predictions of the Rotational and Vibrational Spectra of Molecular Ions written by Youngshang Pak and published by . This book was released on 1996 with total page 536 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Ab Initio Determination of Molecular Properties

Download or read book Ab Initio Determination of Molecular Properties written by Alan Hinchliffe and published by CRC Press. This book was released on 1987 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational quantum chemistry was born in the mid 1960s, and had by the early 1980s achieved considerable status as a structural tool within chemistry. The field has now developed to the point where it has its own journals. However, a major change is taking place in that most consumers of computational quantum chemistry are now experimentalists, who want answers to questions of the type "What if.....?" This change has come about because of the dramatic fall in computer hardware costs, the ready availability of large molecular structure packages and the international collaboration between quantum chemists on a scale rarely witnessed in science. This book aims to show what can be done by computational chemistry, and what kind of reliance might be placed on the predictions. The vast majority of investigations are made at the 'ab initio self consistent field' level, and the results of such calculations occupy a prominent role in this book. However, the user has to be aware of the limitations of this model, and the effects upon electron correlation, etc are discussed. Anyone who is contemplating making use of the techniques of computational quantum chemistry to rationalise or predict chemical behaviour will find this unique book of tremendous use.

Book Vibrational Spectra Conformational Stability Barriers to Internal Rotation and Ab Initio Calculations of Some Three Four and Five membered Ring Molecules

Download or read book Vibrational Spectra Conformational Stability Barriers to Internal Rotation and Ab Initio Calculations of Some Three Four and Five membered Ring Molecules written by Xiang Zhu and published by . This book was released on 1994 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Molecular Vibrational rotational Spectra

Download or read book Molecular Vibrational rotational Spectra written by Dušan Papoušek and published by Elsevier Science & Technology. This book was released on 1982 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Equilibrium Structural Parameters

Download or read book Equilibrium Structural Parameters written by and published by Elsevier Science. This book was released on 1999-12-14 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current volume in the series, Vibrational Spectra and Structure, is a single topic volume on gas phase structural parameters. The title of the volume, Equilibrium Structural Parameters, covers the two most common techniques for obtaining gas phase structural parameters: microwave spectroscopy and the electron diffraction technique. Since the quantum chemical method provides equilibrium geometries, the volume is an attempt to provide a connection between the experimental and theoretical parameters. The book provides a review on molecular structure determinations from spectroscopic data using scaled moments of inertia. The limited number of molecules for which equilibrium parameters have been obtained and the requirement of a large number of microwave data needed to obtain the equilibrium structural parameters is noted. Electron diffraction technique is reviewed, along with a description of how this can incorporate structural information from microwave spectroscopy, vibrational spectroscopy, or theoretical calculations to improve the determination of the structural parameters by electron diffraction studies. Also discussed are the theory and methods of microwave spectroscopy, describing in some detail ro and rs structures as well as rm structures and corrections based on ab initio calculations. The accuracy of the molecular geometry predictions by quantum chemical methods is considered in some detail with data presented in graphic rather than tabular form. This makes it possible to readily note the difference in the parameters predicted at the various levels of quantum mechanical calculations. The four authors have provided a coherent description of the various structural parameters obtained experimentally along with treatments needed to extract equilibrium bond distances and angles.

Book Ab Initio Calculation of Vibrational Circular Dichroism Spectra Using Accurate Post Self Consistent Field Force Fields Trans 2 3 Dideuteriooxirane

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.

Book Molecular Vibrational rotational Spectra

Download or read book Molecular Vibrational rotational Spectra written by Dusan Papousek and published by . This book was released on 1982 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields

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.

Book Computational Molecular Spectroscopy

Download or read book Computational Molecular Spectroscopy written by Per Jensen and published by John Wiley & Sons. This book was released on 2000-11-02 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the use of modern computational methods in predicting high resolution molecular spectra, which allows the experimental spectroscopist to interpret and assign real spectra. * Offers a comprehensive treatment of modern computation techniques. * Provides a collection of material from different areas of theoretical chemistry and physics. * Bridges the gap between traditional quantum chemistry and experimental molecular spectroscopy.