Download or read book Theoretical Modeling of Vibrational Spectra in the Liquid Phase written by Martin Thomas and published by . This book was released on 2017 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theoretical Modeling of Vibrational Spectra in the Liquid Phase written by Martin Thomas and published by Springer. This book was released on 2016-12-24 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis provides a comprehensive description of methods used to compute the vibrational spectra of liquid systems by molecular dynamics simulations. The author systematically introduces theoretical basics and discusses the implications of approximating the atomic nuclei as classical particles. The strengths of the methodology are demonstrated through several different examples. Of particular interest are ionic liquids, since their properties are governed by strong and diverse intermolecular interactions in the liquid state. As a novel contribution to the field, the author presents an alternative route toward infrared and Raman intensities on the basis of a Voronoi tessellation of the electron density. This technique is superior to existing approaches regarding the computational resources needed. Moreover, this book presents an innovative approach to obtaining the magnetic moments and vibrational circular dichroism spectra of liquids, and demonstrates its excellent agreement with experimental reference data.
Download or read book Theoretical Simulation of Nonlinear Spectroscopy in the Liquid Phase written by Thomas la Cour Jansen and published by TLC Publishers. This book was released on 2002 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: PhD thesis on liquid dynamics
Download or read book Novel Approaches to the Structure and Dynamics of Liquids Experiments Theories and Simulations written by Jannis Samios and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unique behavior of the "liquid state", together with the richness of phenomena that are observed, render liquids particularly interesting for the scientific community. Note that the most important reactions in chemical and biological systems take place in solutions and liquid-like environments. Additionally, liquids are utilized for numerous industrial applications. It is for these reasons that the understanding of their properties at the molecular level is of foremost interest in many fields of science and engineering. What can be said with certainty is that both the experimental and theoretical studies of the liquid state have a long and rich history, so that one might suppose this to be essentially a solved problem. It should be emphasized, however, that although, for more than a century, the overall scientific effort has led to a considerable progress, our understanding of the properties of the liquid systems is still incomplete and there is still more to be explored. Basic reason for this is the "many body" character of the particle interactions in liquids and the lack of long-range order, which introduce in liquid state theory and existing simulation techniques a number of conceptual and technical problems that require specific approaches. Also, many of the elementary processes that take place in liquids, including molecular translational, rotational and vibrational motions (Trans. -Rot. -Vib. coupling), structural relaxation, energy dissipation and especially chemical changes in reactive systems occur at different and/or extremely short timescales.
Download or read book Development of first Principles Methods for Modeling Vibrational Spectra in Condensed Phases written by Gregory R. Medders and published by . This book was released on 2015 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the sensitivity of molecular vibrational frequencies and intensities on the surrounding environment, vibrational spectroscopies in principle enable the study of solvation structure and dynamics. Connecting the observed spectral features to a molecular-level picture is, however, often non-trivial. While computer simulations of molecular dynamics represent a potentially powerful tool for developing this molecular-level understanding, the accurate simulation of vibrational spectroscopies in condensed phases poses significant challenges due to the sensitivity of the spectra on both the underlying molecular interactions and the difficulty of obtaining a (statistically meaningful) treatment of the quantum dynamics. In this work, we begin by assessing the ability of different molecular models to reproduce thousands of reference two- and three-body interaction energies calculated at the current "gold standard" level of electronic structure theory, CCSD(T). As described in Chapter 2, these results led us to develop a potential energy surface, named MB-pol, that was fitted exclusively to large datasets of CCSD(T) many-body interaction energies. Crucially, MB-pol was designed to be computationally tractable for condensed phase simulations without sacrificing accuracy. MB-pol reproduces experimental measurements of small cluster properties, as well as thermodynamic and dynamical properties of bulk water at ambient conditions, without containing any empirically derived parameters (Chapter 3). However, unlike the electronic structure calculations to which it is fitted, the MB- pol PES contains no explicit knowledge of the electron distribution, which is required for the calculation of vibrational spectra. To this end, in Chapter 4 we demonstrate that the many-body expansions of the dipole and polarizability also converge for water. Based on this finding, in Chapter 5 we introduce many-body models for the dipole moment and polarizability of water, allowing us to rigorously model IR and Raman spectra from "first principles," through the respective (approximate) quantum time correlation functions. In Chapter 6, we disentangle the contributions of the potential energy and dipole moment surfaces to the IR activity of liquid water. Finally, we conclude in Chapter 7 by reflecting on possible future applications, including the application of the MB-MD approach to the calculation of nonlinear vibrational spectra.
Download or read book Theoretical Vibrational Spectroscopy of the E3B explicit Three body Water Model and Evidence for a Liquid liquid Critical Point in Supercooled Water Within this Model written by and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water, one of the most common substances on earth, is of tremendous importance for our daily life and many disciplines of science. Despite its simple molecular structure, water is very complicated and has many anomalies in condensed phases, mostly due to its vast and continuously changing hydrogen-bonding network. Experimentally, vibrational spectroscopy, especially in the OH bond stretch frequency region, is an ideal tool to investigate the microscopic structure and dynamics of this network. However, the interpretation of the experimental measurements usually needs the assistance of theoretical calculation. This thesis presents our recent work in simulating linear and non-linear vibrational spectroscopy of liquid water in diverse environments using a novel model. We believe our results provide new insights into this important and interesting field. In this thesis, we use a newly developed water model, named E3B, which explicitly includes three-body interaction terms in its Hamiltonian. We begin with the simulation of the two-dimensional sum frequency generation spectroscopy at the water/vapor interface. The result reveals the slow hydrogen-bond switching dynamics at the water liquid/vapor interface. Then we evaluate the E3B model by comparing the temperature dependence of the theoretical non-linear vibrational spectra to experimental data. The result shows that the E3B model outperforms other commonly used models in terms of the microscopic dynamics of liquid water in a wide temperature range. Next, we propose a spectroscopic map for the water bend mode, and use it to study the vibrational spectra of this mode in the bulk liquid and the surface. The result has a reasonable agreement with the experimental data. We suggest that the bend mode, although studied less often than the OH-stretch mode, provides complementary information about the microscopic structure of water. At last, we discuss another interesting topic, which is the proposed liquid-liquid critical point of supercooled water. Using microseconds long simulation, we find evidence for the existence of a LLCP within the E3B model. We rationalize the result of our simulation by connecting this proposed critical point to the kink in the homogeneous nucleation line.
Download or read book Continuum Solvation Models in Chemical Physics written by Benedetta Mennucci and published by John Wiley & Sons. This book was released on 2008-02-28 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the theory and applications of continuum solvation models. The main focus is on the quantum-mechanical version of these models, but classical approaches and combined or hybrid techniques are also discussed. Devoted to solvation models in which reviews of the theory, the computational implementation Solvation continuum models are treated using the different points of view from experts belonging to different research fields Can be read at two levels: one, more introductive, and the other, more detailed (and more technical), on specific physical and numerical aspects involved in each issue and/or application Possible limitations or incompleteness of models is pointed out with, if possible, indications of future developments Four-colour representation of the computational modeling throughout.
Download or read book Advances in Chemical Physics Volume 160 written by Stuart A. Rice and published by John Wiley & Sons. This book was released on 2016-04-11 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Advances in Chemical Physics series provides the chemical physics field with a forum for critical, authoritative evaluations of advances in every area of the discipline. This volume explores the following topics: Thermodynamic Perturbation Theory for Associating Molecules Path Integrals and Effective Potentials in the Study of Monatomic Fluids at Equilibrium Sponteneous Symmetry Breaking in Matter Induced by Degeneracies and Pseudogeneracies Mean-Field Electrostatics Beyond the Point-Charge Description First Passage Processes in Cellular Biology Theoretical Modeling of Vibrational Spectra and Proton Tunneling in Hydroen-Bonded Systems
Download or read book New Approaches to Problems in Liquid State Theory written by Carlo Caccamo and published by Springer Science & Business Media. This book was released on 1999-03-31 with total page 546 pages. Available in PDF, EPUB and Kindle. Book excerpt: The theory of simple and complex fluids has made considerable recent progress, due to the emergence of new concepts and theoretical tools, and also to the availability of a large body of new experimental data on increas ingly complex systems, as well as far-reaching methodological developments in numerical simulations. This AS! aimed at providing a comprehensive overview of the most significant theoretical developments, supplemented by a few presentations of cutting-edge simulation and experimental work. The impact of the Institute in the overall landscape of Statistical Mechanics received an important recognition with its inclusion in the list of satellite events of STATPHYS20, the triennal international conference on Statistical Physics held in Paris in July 1998. These Proceedings contain the texts of the 13 Lecture Courses and 9 Invited Seminars delivered at Patti. Two clear trends emerge from these Proceedings: first, the diversity of new and unexpected theoretical results relating to classic models of liq uids, which have recently been subjected to fresh scrutiny; and secondly the parallel emergence of new concepts, models and methods, aimed at investigating complex fluids and phenomena, like the phase behaviour of fluids in pores, macromolecular assemblies, and the glass transition. Many of the new tools have their roots in traditional liquid state theory, and, in conjunction with fresh input from related fields, allow it wider applicability.
Download or read book Vibrational Spectroscopy of Molecular Liquids and Solids written by S. Bratos and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 461 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book has its or1g1n in a NATO Summer School organized from June 25 to July 7 1979, in Menton, France. The purpose of this School was a comparative study of the various aspects of vibra tional spectroscopy in molecular liquids and solids. This field has been rapidly expanding in the last decade; unfortunately, its development took place independently for liquids and for solids. In these circumstances, the comparison of the basic concepts and techniques used in these two branches of physics appeared as a necessity. The lectures given at the Menton Advanced Study Institute, as well as the exceptionally fruitful and lively discussions which followed them confirmed this point of view. The need of putting together these lectures, in the form of a monograph, clearly appeared during the ASI and the lecturers accepted to write down the material they presented at the Institute, improved thanks to the remarks of the participants. It is the result of this collective work which appears in the familiar Plenum Series.
Download or read book Technical Reports Awareness Circular TRAC written by and published by . This book was released on 1989 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ab Initio Molecular Dynamics written by Dominik Marx and published by Cambridge University Press. This book was released on 2009-04-30 with total page 503 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ab initio molecular dynamics revolutionized the field of realistic computer simulation of complex molecular systems and processes, including chemical reactions, by unifying molecular dynamics and electronic structure theory. This book provides the first coherent presentation of this rapidly growing field, covering a vast range of methods and their applications, from basic theory to advanced methods. This fascinating text for graduate students and researchers contains systematic derivations of various ab initio molecular dynamics techniques to enable readers to understand and assess the merits and drawbacks of commonly used methods. It also discusses the special features of the widely used Car–Parrinello approach, correcting various misconceptions currently found in research literature. The book contains pseudo-code and program layout for typical plane wave electronic structure codes, allowing newcomers to the field to understand commonly used program packages and enabling developers to improve and add new features in their code.
Download or read book Publications of the National Institute of Standards and Technology Catalog written by National Institute of Standards and Technology (U.S.) and published by . This book was released on 1994 with total page 1162 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structural and Vibrational Properties of Liquid Water and Aqueous Solutions from First Principles Molecular Dynamics written by Cui Zhang and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We carried out a series of ab initio molecular dynamics simulations of liquid water and simple ions in water using density functional theory (DFT). Our study had a two-fold objective: (i) establish which level of ab-initio DFT is appropriate to describe not only the structure of water, but also its vibrational, electronic and some of its thermodynamic properties; (ii) interpret experimental data available for infrared spectra (IR) of the pure liquid and liquid solutions. We first studied IR spectra of water using semilocal functionals. We showed that intermolecular dipolar correlations play a key role in determining the complex shape and width of the IR stretching band and those correlations are long-ranged, extending to the second coordination shell. Using a molecular orbital picture, we identified specific features of the band arising from correlations of electronic contributions to the IR activities. These features are robust and do not depend on the functional used in our simulations. The IR spectra of liquid water obtained with the hybrid functional PBE0 yielded a much better agreement with experimental results than a semilocal functional description (PBE). Such an improved description stems from a two-fold effect: a more accurate account, at the PBE0 level of theory, of the vibrational properties of the water monomer and dimer, and an underlying structural model for the liquid with a smaller number of hydrogen bonds and oxygen coordination than those obtained with semilocal functionals. Also with van der Waals density functionals, liquid water displays a hydrogen-bonded network less tightly bound than when using semilocal and hybrid functionals, and yielded IR spectra in good agreement with experiment. However, PBE0 greatly improves the description of water electronic properties (e.g. the quasi-particle gap), while van der Waals functionals yielded results similar to PBE. In spite of improvements in the description of the structural and vibrational properties of water found when using hybrid or van der Waals functionals, our study of the entropy of the liquid indicated that in the vicinity of room temperature and at experimental equilibrium density, all functionals severely underestimate the total entropy and the liquid exhibits a degree of tetrahedral order higher than in experiment. In the case of simple solutions, we focused on anions that are technically more demanding to simulate than cations and in particular on the chloride ion. Compared with the pure liquid, we found an overall softening of the hydrogen bonding structure in the chloride solution, with a smaller average dipole moment of water molecules and an increased number of broken or distorted hydrogen bonds. The ion effects on the hydrogen bonding network are significant in the first chloride solvation shell and become weak beyond that, although non-negligible. Overall, our findings represent a significant step forward in the theoretical modeling of water from first principles, as one may extend the framework adopted here with hybrid or van der Waals functionals to other aqueous environments, such as water under confinement or in contact with surfaces.
Download or read book Vibrational Dynamics Of Molecules written by Joel M Bowman and published by World Scientific. This book was released on 2022-06-14 with total page 603 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vibrational Dynamics of Molecules represents the definitive concise text on the cutting-edge field of vibrational molecular chemistry. The chapter contributors are a Who's Who of world leaders in the field. The editor, Joel Bowman, is widely considered as one of the founding fathers of theoretical reaction dynamics. The included topics span the field, from fundamental theory such as collocation methods and vibrational CI methods, to interesting applications such as astrochemistry, supramolecular systems and virtual computational spectroscopy. This is a useful reference for theoretical chemists, spectroscopists, physicists, undergraduate and graduate students, lecturers and software developers.
Download or read book Glassy Disordered Systems written by Michael I. Klinger and published by World Scientific. This book was released on 2013 with total page 339 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present book describes the fundamental features of glassy disordered systems at high temperatures (close to the liquid-to-glass transition) and for the first time in a book, the universal anomalous properties of glasses at low energies (i.e. temperatures/frequencies lower than the Debye values) are depicted. Several important theoretical models for both the glass formation and the universal anomalous properties of glasses are described and analyzed. The origin and main features of soft atomic-motion modes and their excitations, as well as their role in the anomalous properties, are considered in detail. It is shown particularly that the soft-mode model gives rise to a consistent description of the anomalous properties. Additional manifestations of the soft modes in glassy phenomena are described. Other models of the anomalous glassy properties can be considered as limit cases of the soft-mode model for either very low or moderately low temperatures/frequencies.
Download or read book Chemical Synergies written by Nuno A.G. Bandeira and published by Walter de Gruyter GmbH & Co KG. This book was released on 2018-05-07 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives an overview of recent integrated and inter-disciplinary approaches between chemical experiment and theory in a variety of fields, from polymer science to materials chemistry and ranging from the design of tailored properties to catalysis and reactivity, building on the well-established success of Density Functional Theory as the foremost quantum chemical method to provide qualitative and quantitative interpretation of results from the chemical laboratory. The combination of several characterization techniques with an understanding at the molecular level of chemical and physical phenomena are the main focal point of the subject matter.
