Thermochemistry computational chemistry

Historically, some of those approaches have been developed with a considerable degree of independence, leading to a proliferation of thermochemical concepts and conventions that may be difficult to grasp. Moreover, the past decades have witnessed the development of new experimental methods, in solution and in the gas phase, that have allowed the thermochemical study of neutral and ionic molecular species not amenable to the classic calorimetric and noncalorimetric techniques. Thus, even the expert reader (e.g., someone who works on thermochemistry or chemical kinetics) is often challenged by the variety of new and sophisticated methods that have enriched the literature. For example, it is not uncommon for a calorimetrist to have no idea about the reliability of mass spectrometry data quoted from a paper many gas-phase kineticists ignore the impact that photoacoustic calorimetry results may have in their own field most experimentalists are notoriously unaware of the importance of computational chemistry computational chemists often compare their results with less reliable experimental values and the consistency of thermochemical data is a frequently ignored issue and responsible for many inaccuracies in literature values. 

U. Burkert and N. L. Allinger, Molecular Mechanics, American Chemical Society, Washington, DC 1982 D. W. Rogers, Computational Chemistry Using the PC, 2nd ed., VCH Publishers, New York, 1994, Chapter 10 D. W. Rogers, in Computational Thermochemistry, K. K. Irikura and D. J. Frurip, eds., American Chemical Society, Washington, DC, 1998, Chapter 7 D. M. Hirst, A Computational Approach to Chemistry, Blackwell Scientific Publications, Oxford, UK, 1990, Chapter 3 ... 

The use of computational chemistry to address issues relative to process design was discussed in an article. The need for efficient software for massively parallel architectures was described. Methods to predict the electronic structure of molecules are described for the molecular orbital and density functional theory approaches. Two examples of electronic stracture calculations are given. The first shows that one can now make extremely accurate predictions of the thermochemistry of small molecules if one carefully considers all of the details such as zero-point energies, core-valence corrections, and relativistic corrections. The second example shows how more approximate computational methods, still based on high level electronic structure calculations, can be used to address a complex waste processing problem at a nuclear production facility (Dixon and Feller, 1999). 

Computational chemistry procedures describing the geometry and thermochemistry of gaseous ions are often used to predict and support experimental data. This approach has also been employed to investigate the structure and energetics of some organozinc ions at different levels of theory. Cations and anions having a Zn—C bond which were studied in silico are listed in Tables 6 and 7, respectively. 

For discussions of BSSE and the counterpoise method see (a) Clark T (1985) A handbook of computational chemistry. Wiley, New York, pp 289-301. (b) Martin JM (1998) In Irikura KK, Frurip DJ (eds) Computational thermochemistry. American Chemical Society, Washington, D.C., p 223. (c) References [104] give leading references to BSSE and [104 (a)] describes a method for bringing the counterpoise correction closer to the basis set limit... 

Table 7 Computational Chemistry Books in Crystallography, Spectroscopy, and Thermochemistry...

Dixon, D. A. Feller, D. Peterson, K. A. A practical guide to reliable first principles computational thermochemistry predictions across the periodic table, In Annual Reports in Computational Chemistry Wheeler, R. A., Ed. Elsevier 2012 Vol. 8, p 1-28. 

The two parts of the present volume contain seventeen chapters written by experts from eleven countries. They cover computational chemistry, structural chemistry by spectroscopic methods, luminescence, thermochemistry, synthesis, various aspect of chemical behavior such as application as synthons, acid-base properties, coordination chemistry, redox behavior, electrochemistry, analytical chemistry and biological aspects of the metal enolates. Chapters are devoted to special families of compounds, such as the metal ynolates and 1,2-thiolenes and, besides their use as synthons in organic and inorganic chemistry, chapters appear on applications of metal enolates in structural analysis as NMR shift reagents, catalysis, polymerization, electronic devices and deposition of metals and their oxides. 

Recent advances in computational chemistry have made it possible to calculate enthalpies of formation from quantum mechanical first principles for rather large unsaturated molecules, some of which are outside the practical range of combustion thermochemistry. Quantum mechanical calculations of molecular thermochemical properties are, of necessity, approximate. Composite quantum mechanical procedures may employ approximations at each of several computational steps and may have an empirical factor to correct for the cumulative error. Approximate methods are useful only insofar as the error due to the various approximations is known within narrow limits. Error due to approximation is determined by comparison with a known value, but the question of the accuracy of the known value immediately arises because the uncertainty of the comparison is determined by the combined uncertainty of the approximate quantum mechanical result and the standard to which it is compared. 

Alessandra Ricca received her Ph.D. in chemistry in 1993 from the University of Geneva, Switzerland. Alessandra was a postdoctoral fellow at NASA Ames Research Center with Charles Bauschli-cher and a postdoctoral fellow at Stanford University with Charles Musgrave. In 1998 she joined the Computational Chemistry group at NASA Ames Research Center as a Research Scientist and she is now member of the Computational Nanotechnology group at NASA Ames. Her research interests included transition metal chemistry, spectroscopy, medicinal chemistry, thermochemistry and astrochemistry. Her research efforts are currently devoted to nanotechnology. 

As mentioned above, empirical estimation schemes and computational chemistry calculations provide essential contributions to narrow the gap between the available thermochemical data and the number of molecules for which data have not been experimentally determined. The comprehensive review of these methods is outside the scope of this work. Overviews of representative contributions from empirical schemes " " " and computational chemistry calculations " " to organometallic thermochemistry have recently been published. 

The hrst hve chapters (Part 1) present an overview of some methods that have been used in the recent hterature to calculate rate constants and the associated case studies. The main topics covered in this part include thermochemistry and kinetics, computational chemistry and kinetics, quantum instanton, kinetic calculations in liquid solutions, and new applications of density functional theory in kinetic calculations. The remaining hve chapters (Part II) are focused on apphcations even though methodologies are discussed. The topics in the second part include the kinetics of molecules relevant to combustion processes, intermolecular electron transfer reactivity of organic compounds, lignin model compounds, and coal model compounds in addition to free radical polymerization. 

Advances in computational chemistry and molecular simulation have also reached the stage whereby they can be used to develop more advanced and robust kinetic models for catalytic systems. First-principle quantum chemical methods, for example, are being used to routinely calculate thermochemistry and kinetics for gas phase chemistry with accuracies on the order of... 

Clark et al. had done a masterful job in measuring the heats of combustion, sublimation, and formation for these compounds in the work described in his original paper, only by the expenditure of a great deal of time and effort. And, of course, much time and effort went into the syntheses of these compounds in addition. That the present author was able to conclude that one of the numbers was incorrect and also offer a value for that number from a day or so of computational work certainly impressed Dr. Clark. He accordingly ceased his work in thermochemistry and became a computational chemist. He was later the author of a well-known and widely used early book on computational chemistry. 

Raghavachari K, Curtiss LA (2005) G2, G3 and Associated Quantum Chemical Models for Accurate Theoretical Thermochemistry. In Dykstra CE (ed) Theory and Apphcations of Computational Chemistry The First Forty Years. Elsevier BV, Am-stersdam, p 785... 

The CCCBDB is currently the only computational chemistry or physics database of its kind. This is due to the maturity of quantum mechanics to reliably predict gas-phase thermochemistry for small (20 nonhydrogen atoms or less), primarily organic, molecules, plus the availability of standard-reference-quality experimental data. For gas-phase kinetics, however, only in the past two years have high-quality (<2% precision) rate-constant data become available for H and OH transfer reactions to begin quantifying uncertainty for the quantum mechanical calculation of reaction barriers and tunneling. There is a critical need for comparable quality rate data and theoretical validation for a broader class of gas-phase reactions, as well as solution phase for chemical processing and life science, and surface chemistry. 

Lucius ME, Taylor CR, Hayes CJ. Exploring the thermochemistry of monocychc and bicyclic oxygenated species via computational chemistry methods. In 247th American Chemical Society National Meeting (Poster Session). Dallas, TX. March 2014. 

The Patai Series publishes comprehensive reviews on all aspects of specific functional groups. Each volume contains outstanding surveys on theoretical and computational aspects, NMR, MS, other spectroscopical methods and analytical chemistry, structural aspects, thermochemistry, photochemistry, synthetic approaches and strategies, synthetic uses and applications in chemical and pharmaceutical industries, biological, biochemical and environmental aspects. 

G3 is a recipe involving a variety of different models with the purpose of providing accurate thermochemical data. Original reference (a) L. A. Curtiss, K. Raghavachari, PC. Redfem, V. Rassolov and J.A. Pople, J. Chem. Phys., 109, 7764 (1998). For an up-to-date, on-line source of G3 data see (b) L A. Curtiss, Computational Thermochemistry, chemistry.anl.gov/compmat/ comptherm.htm ... 

The concomitant advances in theoretical methodologies and algorithms have also played a vital role in increasing computational capabilities for theoretical thermochemistry. These advances include (1) new methods for accurate treatment of electron correlation in molecules and atoms such as coupled cluster and quadratic configuration interaction methods, (2) new basis sets such as the correlation consistent basis sets, and (3) development of model chemistry ... 

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