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 Three body Interactions Structure and OH stretch Spectroscopy of the Water Hexamer and Amorphous Solid Water written by and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most common potentials used in classical simulations of liquid water assume a pairwise additive form. Although these models have been very successful in reproducing many properties of liquid water at ambient conditions, none is able to describe water accurately throughout its complicated phase diagram. One reason for this is the neglect of many-body interactions. Three-body interactions arise in condensed phase systems where the electron distribution of a molecule changes depending on the environment. Pairwise additive models include many body effects in a mean field way since they are parameterized to experiments (that have many body effects). Thus, one would not expect them to describe water in heterogeneous environments such as the water-vapor interface. In this thesis, we first present a new simulation model for water that explicitly includes three-body interactions. This model was parameterized to a wide range of physical and dynamical properties. The remainder of this thesis is largely devoted to evaluating the performance of this water model. We first calculate many different properties of water and compare to experimental results. The calculations show an overall improvement compared to the pairwise additive models. The formalism behind lineshape theory is presented and is used in the final chapters to calculate the vibrational spectra of two different systems. The first is the water hexamer. An extensive search of the potential energy surface is performed to find the local minima with respect to the new potential. The energies of the local minima are in qualitative agreement with electronic structure calculations. Analysis of the structures as a function of temperature combined with the vibrational spectra helped us interpret the experimental results. The amorphous phases (of which there are at least two) of water were also studied as a test of the water model. Here, we compared the radial distribution functions and the vibrational spectra to experiments. Finally, the structures of the amorphous phases were compared with those of ice Ih and supercooled water.

Download or read book Thermodynamics and Dynamics of Supercooled Water written by Kevin C. Stokely and published by . This book was released on 2013 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This thesis utilizes the methods of statistical physics and computer simulation to study the thermodynamic and dynamic behavior of liquid water at supercooled temperatures.The behavior of water deviates from that of a simple liquid in a number of remarkable ways, many of which become more apparent as the liquid is supercooled below its equilibrium freezing temperature. Yet, due to nucleation to the crystalline state, a large region of the phase diagram of the supercooled liquid remains unexplored.We make use of a simple model for liquid water to shed light on the behavior of real water in the experimentally inaccessible region. The model predicts a line of phase transitions in the pressure--temperature plane, between high- and low-density forms of liquid water, ending in a liquid-liquid critical point (LLCP). Such a LLCP provides a thermodynamic origin for one of liquid water's anomalies--the rapid rise, and extrapolated divergence, of thermodynamic response functions upon cooling.We find one such response function, the isobaric specific heat, CP , displays two distinct maxima as a function of temperature T in the supercooled region. One maximum is a consequence of the directional nature of hydrogen (H) bonding among molecules; the other is a consequence of the cooperative nature of H bonding. With pressurization, these two maxima move closer in T, finally coinciding at the LLCP. This suggests that measurement of CP far from any LLCP could provide evidence for the existence of water's LLCP.Recent experiments find that the T- dependence of the characteristic time for H bond rearrangement displays three distinct regimes. Our observed behavior of CP , combined with Adam-Gibbs theory, allows for a thermodynamic interpretation of this feature of water's dynamics. The dynamics of the model are also measured directly by a Monte Carlo procedure, and are found in agreement with experiment.Further, the model allows the directional and cooperative components of the H bond interaction to be varied independently. By varying only these two energy scales, the low-T phase diagram changes dramatically, exhibiting one of several previously proposed thermodynamic scenarios. Our results link each of these scenarios, by recognizing the energetics of the H bond as the underlying physical mechanism responsible for each.

Download or read book Theory of Supercooled Liquids Phase Diagram of Water Orientational Dependent Interactions written by Paul H. E. Meijer and published by . This book was released on 1970 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: Part 1: We investigated the question whether one can conclude from BBGKY theories whether instabilities do occur in a liquid at low temperatures. Several authors denied this possibility and we show that such results are due to the assumptions they made. Part 2: In order to calculate the phase diagram of water we introduce a lattice model that has the following features. A nearest neighbor attraction, which is strongly dependent on the relative orientation of water molecules, due to hydrogen bonding and a next nearest neighbor or three body repulsion. The hydrogen bonding is introduced with the help of a set of weight factors in accordance with Pauling's ice rules. The entropy is calculated according to the cluster variation method for tetrahedrons. The isotherms show a maximum in the density and a phase separation between the vapor, the open ice state and a state which is dense packed. Part 3: To see how orientational dependent forces influence the supercooling process, the simplest model known (Barker and Fock model) is analysed. It is shown under what conditions the phase diagram becomes topologically different from the simple Ising phase diagram. Part 4: Preparatory work for the determination of the characteristic points in the phase diagram of an antiferromagnet. (Author).

Download or read book Analysis Simulation of Dynamics in Supercooled Liquids written by Yael Sarah Elmatad and published by . This book was released on 2011 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: The nature of supercooled liquids and the glass transition has been debated by many scientists. Several theories have been put forth to describe the remarkable properties of this out-of-equilibrium material. Each of these theories makes specific predictions as to how the scaling of various transport properties in supercooled materials should behave. Given access to a large pool of high-quality supercooled liquid data we seek to compare these theories to one another. Moreover, we explore properties of a pair of models which are the basis for one particularly attractive theory - Chandler-Garrahan theory - and discuss the models' behavior in space-time and possible implications to the behavior of experimental supercooled liquids. Here we investigate the nature of dynamics in supercooled liquids using a two pronged approach. First we analyze the transport properties found in experiments and simulations of supercooled liquids. Then, we analyze simulation trajectories for lattice models which reproduce many of the interesting properties of supercooled liquids. In doing so, we illuminate several glass universalities, common properties of a wide variety of glass formers. By analyzing relaxation time and viscosity data for over 50 data sets and 1200 points, we find that relaxation time can be collapsed onto a single, parabolic curve. This collapse supports a theory of universal glass behavior based on facilitated models proposed by David Chandler and Juan Garrahan in 2003. We then show that the parabolic fit parameters for any particular liquid are a material property: they converge fast and are capable of predicting behavior in regions beyond the included data sets. We compare this property to other popular fitting schemes such as the Vogel-Fulcher, double exponential, and fractional exponential forms and conclude that these three forms result in parameters which are non predictive and therefore not material properties. Additionally, we examine the role of attractive forces in liquids by comparing simulations of a Lennard-Jones mixture, which contains both attractions and repulsions, with that of a Weeks-Chandler-Andersen mixture, which only retains repulsive forces. We show that within the framework of the parabolic collapse, these two liquids behave identically. This suggests that attractive forces do not play a key role in glassy dynamics. Rather, repulsive forces - as has been shown in dense liquids - play the largest contributing role in jamming systems into glassy states. We further investigate the predicted fragile-to-strong crossover in glass formers and find no compelling evidence for the crossover in bulk materials at this time. Additionally, we study ensembles of trajectories for a specific class of kinetically constrained models which reproduce the dynamic heterogeneity found in real glass formers. The one dimensional models we consider are the Fredrickson-Andersen (FA) model and the east model. These two models have been shown to behave as supercooled liquids reproducing properties such as the breakdown of the Stokes-Einstein equation relating diffusion constants and relaxation times. We use transition path sampling in the s-ensemble to bias the system into low activity regions. It has been previously shown that the FA model goes through a first-order dynamical phase transition in trajectory space. We extend this to include a slightly softened FA model, which we believe to be more representative of atomistic systems. We have determined that this first order coexistence line ends in a critical point where the surface tension between active and inactive trajectories in space-time disappears. Beyond this region as the softened FA model becomes unconstrained, the transition disappears and no phase transition is detected. Beyond simulations, these results were verified by analytical methods. This verification was achieved by mapping of soft FA model onto a model which undergoes a quantum phase transition. Beyond the FA model, we consider the softened east model. Unlike the FA model, however, the east model relaxes hierarchically and has a particular directionality. Many of the same conclusions - such as the appearance of a non-trivial critical point in space time - appear in the east model. Moreover, many of the same analytical tools can be used to determine the symmetry line that separates the active and inactive phases. However, the exact mapping of the critical point location is unknown and the location of the critical point is determined numerically. We also investigate how the inactive phase created by applying a dynamical field relaxes to the active state under no external field and find that the process appears barrierless. Lastly, we propose current and ongoing work which seeks to understand how to numerically quantify the degree to which a system is dynamically facilitated by looking at multipoint correlation functions of endured kinks. We contrast this method with previously suggested methods based on locating avalanches by testing both methods on kinetically constrained models such as the east and FA models.

Download or read book Molten Salt Technology written by David G. Lovering and published by Springer. This book was released on 2014-11-14 with total page 536 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physical Control Methods in Plant Protection written by Charles Vincent and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: Jointly published with INRA, Paris. Pesticide resistance is becoming more frequent and widespread with more than 500 insect species known to have become resistant to synthetic insecticides. On the other hand, consumers increasingly demand agricultural products without any pesticide residues. This book, for the first time, shows the alternative: solely physical methods for plant protection by means of thermal, electromagnetic, mechanical and vacuum processes. A glossary rounds up this extremely valuable book.

Download or read book Ultrafast Infrared Vibrational Spectroscopy written by Michael D. Fayer and published by CRC Press. This book was released on 2013-03-04 with total page 491 pages. Available in PDF, EPUB and Kindle. Book excerpt: The advent of laser-based sources of ultrafast infrared pulses has extended the study of very fast molecular dynamics to the observation of processes manifested through their effects on the vibrations of molecules. In addition, non-linear infrared spectroscopic techniques make it possible to examine intra- and intermolecular interactions and how such interactions evolve on very fast time scales, but also in some instances on very slow time scales. Ultrafast Infrared Vibrational Spectroscopy is an advanced overview of the field of ultrafast infrared vibrational spectroscopy based on the scientific research of the leading figures in the field. The book discusses experimental and theoretical topics reflecting the latest accomplishments and understanding of ultrafast infrared vibrational spectroscopy. Each chapter provides background, details of methods, and explication of a topic of current research interest. Experimental and theoretical studies cover topics as diverse as the dynamics of water and the dynamics and structure of biological molecules. Methods covered include vibrational echo chemical exchange spectroscopy, IR-Raman spectroscopy, time resolved sum frequency generation, and 2D IR spectroscopy. Edited by a recognized leader in the field and with contributions from top researchers, including experimentalists and theoreticians, this book presents the latest research methods and results. It will serve as an excellent resource for those new to the field, experts in the field, and individuals who want to gain an understanding of particular methods and research topics.

Download or read book Concepts and Methods of 2D Infrared Spectroscopy written by Peter Hamm and published by Cambridge University Press. This book was released on 2011-02-24 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: 2D infrared (IR) spectroscopy is a cutting-edge technique, with applications in subjects as diverse as the energy sciences, biophysics and physical chemistry. This book introduces the essential concepts of 2D IR spectroscopy step-by-step to build an intuitive and in-depth understanding of the method. This unique book introduces the mathematical formalism in a simple manner, examines the design considerations for implementing the methods in the laboratory, and contains working computer code to simulate 2D IR spectra and exercises to illustrate involved concepts. Readers will learn how to accurately interpret 2D IR spectra, design their own spectrometer and invent their own pulse sequences. It is an excellent starting point for graduate students and researchers new to this exciting field. Computer codes and answers to the exercises can be downloaded from the authors' website, available at www.cambridge.org/9781107000056.

Download or read book The Physics and Physical Chemistry of Water written by Felix Franks and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 610 pages. Available in PDF, EPUB and Kindle. Book excerpt: to arrive at some temporary consensus model or models; and to present reliable physical data pertaining to water under a range of conditions, i.e., "Dorsey revisited," albeit on a less ambitious scale. I should like to acknowledge a debt of gratitude to several of my col leagues, to Prof. D. J. G. Ives and Prof. Robert L. Kay for valuable guidance and active encouragement, to the contributors to this volume for their willing cooperation, and to my wife and daughters for the understanding shown to a husband and father who hid in his study for many an evening. My very special thanks go to Mrs. Joyce Johnson, who did all the cor respondence and much of the arduous editorial work with her usual cheerful efficiency. F. FRANKS Biophysics Division Unilever Research Laboratory ColworthjWelwyn Colworth House, Sharnbrook, Bedford March 1972 Contents Chapter 1 Introduction-Water, the Unique Chemical F. Franks I. lntroduction ........................................ . 2. The Occurrence and Distribution of Water on the Earth 2 3. Water and Life ...................................... 4 4. The Scientific Study of Water-A Short History ........ 8 5. The Place of Water among Liquids . . . . . . . . . . . . . . . 13 . . . . . Chapter 2 The Water Moleeule C. W. Kern and M. Karplus 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 . . . . . . . . . . 2. Principles of Structure and Spectra: The Born-Oppenheimer Separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 . . . . . . . . . . . . 3. The Electronic Motion ............................... 26 3.1. The Ground Electronic State of Water ............ 31 3.2. The Excited Electronic States of Water ........... 50 4. The Nuclear Motion ................................. 52 5. External-Field Effects ................................. 70 5.1. Perturbed Hartree-Fock Method . . . . . . . . . . . . . . . 74 . . .

Download or read book Specific Ion Effects written by Werner Kunz and published by World Scientific. This book was released on 2010 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: Specific ion effects are important in numerous fields of science and technology. This book summarizes the main ideas that came up over the years. It presents the efforts of theoreticians and supports it by the experimental results stemming from various techniques.

Download or read book Solvation Thermodynamics written by Arieh Y. Ben-Naim and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with a subject that has been studied since the beginning of physical chemistry. Despite the thousands of articles and scores of books devoted to solvation thermodynamics, I feel that some fundamen tal and well-established concepts underlying the traditional approach to this subject are not satisfactory and need revision. The main reason for this need is that solvation thermodynamics has traditionally been treated in the context of classical (macroscopic) ther modynamics alone. However, solvation is inherently a molecular pro cess, dependent upon local rather than macroscopic properties of the system. Therefore, the starting point should be based on statistical mechanical methods. For many years it has been believed that certain thermodynamic quantities, such as the standard free energy (or enthalpy or entropy) of solution, may be used as measures of the corresponding functions of solvation of a given solute in a given solvent. I first challenged this notion in a paper published in 1978 based on analysis at the molecular level. During the past ten years, I have introduced several new quantities which, in my opinion, should replace the conventional measures of solvation thermodynamics. To avoid confusing the new quantities with those referred to conventionally in the literature as standard quantities of solvation, I called these "nonconventional," "generalized," and "local" standard quantities and attempted to point out the advantages of these new quantities over the conventional ones.

Download or read book The Properties of Energetic Materials written by Mohammad Hossein Keshavarz and published by Walter de Gruyter GmbH & Co KG. This book was released on 2017-11-20 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: For a chemist who is concerned with the synthesis of new energetic compounds, it is essential to be able to assess physical and thermodynamic properties, as well as the sensitivity, of possible new energetic compounds before synthesis is attempted. Various approaches have been developed to predict important aspects of the physical and thermodynamic properties of energetic materials including (but not limited to): crystal density, heat of formation, melting point, enthalpy of fusion and enthalpy of sublimation of an organic energetic compound. Since an organic energetic material consists of metastable molecules capable of undergoing very rapid and highly exothermic reactions, many methods have been developed to estimate the sensitivity of an energetic compound with respect to detonationcausing external stimuli such as heat, friction, impact, shock and electrostatic discharge. This book introduces these methods and demonstrates those methods which can be easily applied.

Download or read book Cryogenic Mixed Refrigerant Processes written by Gadhiraju Venkatarathnam and published by Springer Science & Business Media. This book was released on 2008-12-10 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most conventional cryogenic refrigerators and liquefiers operate with pure fluids, the major exception being natural gas liquefiers that use mixed refrigerant processes. The fundamental aspects of mixed refrigerant processes, though very innovative, have not received the due attention in open literature in view of commercial interests. Hundreds of patents exist on different aspects of mixed refrigerant processes. However, it is difficult to piece together the existing information to choose an appropriate process and an optimum composition or a given application. The aim of the book is to teach (a.) the need for refrigerant mixtures, (b.) the type of mixtures that can be used for different refrigeration and liquefaction applications, (c.) the different processes that can be used and (d.) the methods to be adopted for choosing the components of a mixture and their concentration for different applications.

Download or read book Valency and Bonding written by Frank Weinhold and published by Cambridge University Press. This book was released on 2005-06-17 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first modernized overview of chemical valency and bonding theory, based on current computational technology.

Download or read book Water written by Julian Caldecott and published by Random House. This book was released on 2008-09-04 with total page 291 pages. Available in PDF, EPUB and Kindle. Book excerpt: All known forms of life depend on water. Covering 71 per cent of the Earth's surface, water seems to be plentiful. But there are 1.2 billion people who currently live without a safe water supply, the amount of available drinking water is shrinking and the need for it is increasing relentlessly. While some regions are receiving too much rain, others are receiving too little. We are approaching a global water emergency. Julian Caldecott examines the vital role this fascinating substance plays on our planet and explores the historical, scientific, political and economic reasons behind the looming water crisis. He reveals where the water we use comes from, and at what social and environmental cost. This is an intriguing and sometimes unsettling portrait of the future of water in our changing world and what we can all do to make a difference.

Download or read book Nonlinear Wave Processes in Excitable Media written by Arunn V. Holden and published by Springer. This book was released on 2013-12-21 with total page 511 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of a NATO ARW held in Leeds, UK, September 11-15, 1989