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 Understanding Vibrational Spectroscopy in Complex Environments Through First Principles Modeling written by Jeffrey Becca and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Vibrational spectroscopy takes many forms, from techniques like Raman scattering to sum frequency generation. These techniques involve measuring the energy difference between the incident light and scattered light. Vibrational spectroscopy has the advantage that virtually any system can scatter light, while techniques like fluorescence spectroscopy that requires a molecule to be able to absorb and emit light. The main disadvantage of Raman spectroscopy is that the intensity of the process is much weaker than that of absorption and emission processes like fluorescence. In recent times, vibrational techniques have been paired with strong electric fields created by plasmonic resonances from metal surfaces and nanoparticles. These techniques are known as surface enhanced spectroscopy. Surface enhanced Raman scattering (SERS) has been used to study processes that are far too weak for normal Raman scattering, such as single molecule detection. While the pairing of plasmonic systems with Raman and other vibrational spectroscopies has been fruitful, the surface-enhanced techniques add complexity to understanding and simulating the resulting vibrational spectroscopy. Ideally, simulations would be capable of modeling the molecular species, the plasmonic metal system, and any solvent that may be in the experimental setup. Even for relatively quick first principles techniques like Density Functional Theory (DFT), systems of this size are far too great to simulate in any reasonable time frame. One way of overcoming this limit is to model the most important features of the system, usually the molecular target, with first principle techniques while including the relevant environmental effects with more approximate methods. However, careful consideration must be given to which environment effects are included into the simulations and what approximations are used. In SERS and other similar surface-enhanced techniques, the largest enhancement comes from the strong electric fields created from the plasmonic metals in which the molecule resides. While correctly modeling the intensity of the local electric fields is important to SERS, spectral changes often occur in surface-enhanced techniques due to other factors. These spectral changes occur because the molecule's electronic structure is not isolated from its environment. Adsorption to a surface or specific interactions with solvent often alter the electronic structure of the molecule enough that the resulting spectra is no longer the same as normal Raman scattering. This means that if the metal surface or solvent plays a significant role in experiment and it is not accounted for in an accurate enough manor, the resulting simulated spectra will not be correct. For these reasons, understanding which processes are important to the chemical species is a strong desire for the surface-enhanced spectroscopy community. In this work, various systems were simulated using different methods, which depended on the complexity required and the environmental effects that were included. First, doubly resonant infrared-visible sum frequency generation (DR-IVSFG) was simulated for a push-pull azobenzene compound. We show through our work that by tuning the visible laser, different spectral bands are selected and track along with the changing energy. This result was found by modeling two confirmations of the azobenzene compound with vibronic effects included through a Herzberg-Teller term. The resulting tracking nature was due to probing two different states in different confirmations of azobenze on the film, a low energy tracking of the \emph{cis} isomer and high energy tracking of the \emph{trans} isomer. Second, this work demonstrates how, combined with experiment, new surface enhanced Raman spectroscopy (SERS) ligands can be profiled. A group of different N-heterocyclic carbenes were simulated which elucidated binding characteristics and SERS spectral signatures. We demonstrated that using time-dependent density functional theory to simulate a Au20 nanocluster and carbene system could reproduce experimental SERS spectra. We also showed that the binding interaction of the carbene and the gold cluster is relatively strong, since the stable Au20 structure was perturbed enough by the carbene to raise an atom from the surface in an adatom-like configuration. Our simulations also showed agreement with experiment throughout various deuterated carbenes, with some deuterated species emphasizing the functional group contribution to the SERS spectra. In the next chapter, we continued the N-heterocyclic carbene studies in order to simulate the functionalization of carbene ligands already attached to the surface. We showed proof of modifying a NO$_2$ group to a NH$_2$ and ND$_2$ group depending on the reaction conditions, which was confirmed by experimental SERS measurements. This work also discusses the implementation of a Discrete Interaction Model / Quantum Mechanics (DIM/QM) method that includes explicit solvent molecules in SERS simulations. This implementation was used to study the effects that solvent has on the image and local electric fields near a pyridine molecule in a solvated nanoparticle junction, and an observation about how those fields change from normal Raman scattering and SERS in solution. We observed that for normal Raman scattering in solution, the solvent molecules had an overall screening effect, lowering the intensity of the Raman spectra. However, solution phase SERS shows an enhancement that does not exist without the solvent. This enhancement comes from increasing the near field generated by the plasmonic nanoparticle junction, leading to more intense and inhomogeneous electric fields. We also show that the SERS enhancement that arises from the solvent is large enough to rival the enhancement seen from the chemical enhancement mechanism and should be accounted for in simulations. By understanding these different ways that spectral signals can be altered by molecular interactions with their environment, this work has built a foundation of better understanding surface enhanced spectroscopies.

Download or read book Theoretical Study of Single molecule Spectroscopy and Vibrational Spectroscopy in Condensed Phases written by Shilong Yang and published by . This book was released on 2005 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) To interpret the fluorescence measurements of the mechanical properties of double-stranded DNA, a worm-like chain model is used as a first-principle model to study double-stranded DNA under hydrodynamic flows. The second part of the thesis concentrates on nonperturbative vibrational energy relaxation (VER) effects of vibrational line shapes. In general, nonperturbative and non-Markovian VER effects are demonstrated more strongly on nonlinear vibrational line shapes than on linear absorption.

Download or read book Vibrational Spectroscopy written by D. N. Sathyanarayana and published by New Age International. This book was released on 2015-07 with total page 720 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vibrational Spectroscopy Provides In A Very Readable Fashion A Comprehensive Account Of The Fundamental Principles Of Infrared And Raman Spectroscopy For Structural Applications To Inorganic, Organic And Coordination Compounds. Theoretical Analyses Of The Spectra By Normal Coordinate Treatment, Factor Group Analysis And Molecular Mechanics Are Delineated.The Book Features: * Coverage From First Principles To Recent Advances * Relatively Self-Contained Chapters * Experimental Aspects * Step By Step Treatment Of Molecular Symmetry And Group Theory * Recent Developments Such As Non-Linear Raman Effects * Comprehensive Treatment Of Rotation Spectroscopy * Band Intensities * Spectra Of Crystals * End-Of-Chapter Exercises.Suitable For Students And Researchers Interested In The Field Of Vibrational Spectroscopy. No Prior Knowledge Of Concepts Specific To Vibrational Spectroscopy Is Necessary. Mathematical Background Such As Matrices And Vectors Are Provided.

Download or read book Modeling Phase and Sorption Equilibria Using First Principles Simulations written by Himanshu Goel and published by . This book was released on 2018 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: To capture the underlying chemistry and physics of a system on electronic structure platform, it is necessary to accurately describe the intermolecular interactions such as repulsion, polarization, hydrogen bonding, and van der Waals interactions. Among these interactions, van der Waals (dispersion) interactions are weak in nature as compare to covalent bonds and hydrogen bonding, but it is physically and chemically very important in accurately predicting condensed phase properties such as vapor liquid equilibria(VLE). This presents a significant challenge in modeling VLE using a first principles approach. However, recent developments in dispersion corrected (DFT-D3) and nonlocal density functionals can model dispersion interactions with reasonable accuracy. Here, we will present some of the results that quantify the efficacy of recent density functionals in predicting phase equilibria of molecular systems via first principle Monte Carlo (FPMC) simulations. Our aim is to assess the performance of several density functional by determining VLE, critical properties, dimer potential energy curves, vibrational spectra, and structural properties. The functional used in our study includes PBE-D3, BLYP-D3, rVV10, PBE0-D3, and M062X-D3. In addition, we have used the second order Møller-Plesset perturbation theory (MP2) method for computing the density of argon at a single temperature. The organic compounds considered for this study involves argon, CO2, SO2, and various hydroflurocarbons (R14, R134a, CF3H, CF2H2, CFH3) molecules. Additionally, the development of new materials, ionic liquids, and modification of industrial processes are an ongoing effort by researchers to efficiently capture acidic gases. Our ability to model these sorption processes using a first principles approach can have a significant impact in speeding up the discovery process. In our work, we have predicted CO2 solubility in triethyl(butyl)phosphonium ionic liquid via FPMC simulations. Our results reveal the infrared spectra, structural and transport properties for pure ionic liquid and its mixture with CO2 through ab initio molecular dynamics simulations.

Download or read book Modeling Phase and Sorption Equilibria Using First Principles Simulations written by and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To capture the underlying chemistry and physics of a system on electronic structure platform, it is necessary to accurately describe the intermolecular interactions such as repulsion, polarization, hydrogen bonding, and van der Waals interactions. Among these interactions, van der Waals (dispersion) interactions are weak in nature as compare to covalent bonds and hydrogen bonding, but it is physically and chemically very important in accurately predicting condensed phase properties such as Vapor liquid equilibria. This presents a significant challenge in modeling VLE using a first principles approach. However, recent developments in dispersion corrected (DFT-D3) and nonlocal density functionals can model dispersion interactions with reasonable accuracy. Here, we will present some of results that quantify efficacy of recent density functionals in predicting phase equilibria of molecular systems via first principle Monte Carlo (FPMC) simulations. Our aim is to assess the performance of several density functional by determining VLE, critical properties, dimer potential energy curves, vibrational spectra, and structural properties. The functional used in our study includes PBE-D3, BLYP-D3, rVV10, PBE0- D3, and M062X-D3. In addition, we have used the second order Møller-Plesset perturbation theory (MP2) method for computing density of argon at single temperature. The organic compounds considered for this study involves argon, CO2, SO2, and various hydroflurocarbons (R14, R134a, CF3H, CF2H2, CFH3) molecules. Additionally, the development of new materials, ionic liquids, and modification of industrial processes are an ongoing effort by researchers to efficiently capture acidic gases. Our ability to model these sorption processes using a first principles approach can have significant impact in speeding up the discovery process. In our work, we have predicted CO2 solubility in triethyl(but

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 602 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Download or read book Annual Reports in Computational Chemistry written by Ralph A. Wheeler and published by Elsevier. This book was released on 2014-12-03 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annual Reports in Computational Chemistry provides timely and critical reviews of important topics in computational chemistry as applied to all chemical disciplines. Topics covered include quantum chemistry, molecular mechanics, force fields, chemical education, and applications in academic and industrial settings. Focusing on the most recent literature and advances in the field, each article covers a specific topic of importance to computational chemists. Quantum chemistry Molecular mechanics Force fields Chemical education and applications in academic and industrial settings

Download or read book Computational Strategies for Spectroscopy written by Vincenzo Barone and published by John Wiley & Sons. This book was released on 2011-11-01 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational spectroscopy is a rapidly evolving field that is becoming a versatile and widespread tool for the assignment of experimental spectra and their interpretation as related to chemical physical effects. This book is devoted to the most significant methodological contributions in the field, and to the computation of IR, UV-VIS, NMR and EPR spectral parameters with reference to the underlying vibronic and environmental effects. Each section starts with a chapter written by an experimental spectroscopist dealing with present challenges in the different fields; comprehensive coverage of conventional and advanced spectroscopic techniques is provided by means of dedicated chapters written by experts. Computational chemists, analytical chemists and spectroscopists, physicists, materials scientists, and graduate students will benefit from this thorough resource.

Download or read book Basic Features Of The Glassy State Proceedings Of The Second International Workshop On Non crystalline Solids written by A Alegria and published by World Scientific. This book was released on 1990-06-09 with total page 597 pages. Available in PDF, EPUB and Kindle. Book excerpt: This proceedings cover the basic aspects and technical applications of non-crystalline solids from experts in different fields like polymer science, metallic glasses, basic properties, technological applications etc.

Download or read book Handbook of Vibrational Spectroscopy 5 Volume Set written by John M. Chalmers and published by Wiley-Blackwell. This book was released on 2002-02-15 with total page 962 pages. Available in PDF, EPUB and Kindle. Book excerpt: THE DEFINITIVE RESOURCE The first truly comprehensive work on vibrational spectroscopy, providing a one-stop reference for infrared, near-infrared and Raman spectroscopy. AUTHORITATIVE, ... With contributions from acknowledged leaders in the field, the calibre of the editors and authors speaks for itself. Volume 1: Theory and Instrumentation Volume 2: Sampling Techniques Volume 3: Sample Characterization and Spectral Data Processing Volume 4: Applications in Industry, Materials and the Physical Sciences Volume 5: Applications in Life, Pharmaceutical and Natural Sciences COMPREHENSIVE, ... Covering all aspects of infrared, near-infrared and Raman spectroscopy the five volumes also include coverage of associated techniques, such as inelastic neutron scattering, electron energy loss and cavity ringdown spectroscopy. AND ON YOUR WAVELENGTH. Each of the extensively referenced articles comprises a brief introduction as well as in-depth coverage of the subject. The result... a resource that will be useful for both the beginner to the field as well as the expert.

Download or read book New Perspectives on Mineral Nucleation and Growth written by Alexander E.S. Van Driessche and published by Springer. This book was released on 2016-12-20 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last decade, numerous studies have demonstrated the existence of alternative pathways to nucleation and crystallisation that oppose the classical view. Such proposed scenarios include multistage reactions proceeding via various precursor species and/or intermediate phases. The aim of this book is to review and discuss these recent advances in our understanding of the early stages of mineralisation through a series of contributions that address both experimental and theoretical studies about the formation and nature of initial precursor species (e.g., prenucleation clusters, dense liquid phases, amorphous nanoparticles, etc.) as well as their transformations leading to the stable mineral phase. Several chapters are devoted to cutting-edge analytical techniques used for investigating the above processes in situ, in real time and at conditions relevant to both natural and industrial processes. At the end of the book, the editors summarize the key questions that still need to be addressed in order to establish a complete picture of the nucleation and growth processes involved during the formation of minerals

Download or read book Classical And Quantum Dynamics In Condensed Phase Simulations Proceedings Of The International School Of Physics written by Bruce J Berne and published by World Scientific. This book was released on 1998-06-17 with total page 881 pages. Available in PDF, EPUB and Kindle. Book excerpt: The school held at Villa Marigola, Lerici, Italy, in July 1997 was very much an educational experiment aimed not just at teaching a new generation of students the latest developments in computer simulation methods and theory, but also at bringing together researchers from the condensed matter computer simulation community, the biophysical chemistry community and the quantum dynamics community to confront the shared problem: the development of methods to treat the dynamics of quantum condensed phase systems.This volume collects the lectures delivered there. Due to the focus of the school, the contributions divide along natural lines into two broad groups: (1) the most sophisticated forms of the art of computer simulation, including biased phase space sampling schemes, methods which address the multiplicity of time scales in condensed phase problems, and static equilibrium methods for treating quantum systems; (2) the contributions on quantum dynamics, including methods for mixing quantum and classical dynamics in condensed phase simulations and methods capable of treating all degrees of freedom quantum-mechanically.

Download or read book Two Dimensional Optical Spectroscopy written by Minhaeng Cho and published by CRC Press. This book was released on 2009-06-16 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-Dimensional Optical Spectroscopy discusses the principles and applications of newly emerging two-dimensional vibrational and optical spectroscopy techniques. It provides a detailed account of basic theory required for an understanding of two-dimensional vibrational and electronic spectroscopy. It also bridges the gap between the formal developm

Download or read book Handbook of Vibrational Spectroscopy written by John M. Chalmers and published by . This book was released on 2002 with total page 634 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Atomic Molecular and Optical Physics written by and published by Academic Press. This book was released on 2009-08-04 with total page 457 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume continues the tradition of the Advances series. It contains contributions from experts in the field of atomic, molecular, and optical (AMO) physics. The articles contain some review material, but are intended to provide a comprehensive picture of recent important developments in AMO physics. Both theoretical and experimental articles are included in the volume. International experts Comprehensive articles New developments

Download or read book Computational Quantum Physics and Chemistry of Nanomaterials written by Mojmír Šob and published by MDPI. This book was released on 2021-04-01 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Special Issue of Nanomaterials collects a series of original research articles providing new insight into the application of computational quantum physics and chemistry in research on nanomaterials. It illustrates the extension and diversity of the field and indicates some future directions. It provides the reader with an overall view of the latest prospects in this fast evolving and cross-disciplinary field