Quantum-chemical prediction

Quantum chemical predictions of tautomeric equilibria Ab initio multireference Cl studies of tautomers UPS spectra Combined approach to the tautomerism in azaaromatic heterocycles by N, C, and H NMR Fluoro-azoles Experimental data and MNDO studies Tautomerism A review... 

In contrast to kinetic models reported previously in the literature (18,19) where MO was assumed to adsorb at a single site, our preliminary data based on DRIFT results suggest that MO exists as a diadsorbed species with both the carbonyl and olefin groups being coordinated to the catalyst. This diadsorption mode for a-p unsaturated ketones and aldehydes on palladium have been previously suggested based on quantum chemical predictions (20). A two parameter empirical model (equation 4) where - rA refers to the rate of hydrogenation of MO, CA and PH refer to the concentration of MO and the hydrogen partial pressure respectively was developed. This rate expression will be incorporated in our rate-based three-phase non-equilibrium model to predict the yield and selectivity for the production of MIBK from acetone via CD. 

A correct description of Pauli repulsive interactions between valence, subvalence, and core electrons as well as of electrostatic interactions is an essential requirement for accurate quantum chemical predictions. We now show that a proper analysis of steric repulsion—Pauli repulsion in nonbonded... 

Figure 1 Thermodynamic cycle for the enthalpy of formation of methane (CH4) from the standard states of carbon and hydrogen (graphite and H2). The quantities in italics are calculated in typical thermochemical quantum chemical predictions.

In contrast with empirical models, quantum chemical methods do not provide adjustable force constants. It is therefore not unexpected that quantitative discrepancies appear when quantum chemical predictions are compared in detail with the results of NRVS measurements. NRVS results thus provide a benchmark for development of quantum chemical methods for transition metal systems. Using quantum chemical results as starting input in empirical calculations may be a valuable approach for future work. Meanwhile, however, reproduction is sufficiently accurate to guide the understanding of observed vibrational features. Mode descriptions given in the previous section largely rely on comparison with quantum chemical predictions. 

The sub-Angstrom resolution of the transition state d3mamics of a chemical reaction obtained using force-clamp techniques makes a novel contribution to our understanding of protein-based chemical reactions. These experiments, combined with quantum chemical predictions of transition state structure, hold promise for developing a quantitative view of enz3mie catalysis and other protein-based chemical reactions, at a resolution currently unattainable by any other means. 

During the last 10 years, remarkable progress has been made in devising efficient procedures for accurate electronic structure calculations. Not only have the size and complexity of the problems which can be handled been extended, but also the reliability of quantum-chemical results has been considerably improved. Accurate quantum-chemical predictions of properties for small molecules have proven that theoretical calculations are often a useful complement to modern experimental work . 

In spite of great interest in preparation and studying of silver clusters Ag , their structures are not clearly determined yet. Thus, only structures of clusters with n=3,4,5 are fairly well established. The most effective method of investigations of clusters structures is a comparison of quantum chemical predictions for different stable geometries with experimental data. The central problem in reliable identification of clusters structures by this method is an increase of the amount of structures characterized by closely allied values of energetic characteristics as the size of the cluster grows. As a consequence, structural assigmnent even for relatively simple clusters is a very difficult problem [1]. 

C. Importance of Correlation Energy for Quantum Chemical Predictions - - 34... 

It thus remains to discuss the inclusion of groups 11 and 12. The group 11 elements Cu, Ag, Au, and Rg clearly have a too pronounced involvement of their (n —1) d-orbitals in bonding, even in their lower oxidation states, to be safely considered main-group elements. The group 12 elements Zn, Cd, Hg, and Cn are usually considered to be main-group or post-transition elements. Yet recently quantum-chemical predictions [5] of oxidation-state Hg(-l-IV) in the form of the... 

Fu Y, Liu L, Yu HZ, Wang YM, Guo QX (2005) Quantum-chemical predictions of absolute standard redox potentials of diverse organic molecules and free radicals in acetonitrile. J Am Chem Soc 127 7227... 

ABSTRACT. The geometries of inclusion complexes of a-cyclodextrin(a-CD) with guests, benzoic acid, p-hydroxy benzoic acid, and p-nitrophenol in aqueous solution have been determined by comparing the complexation induced C-13 shifts of guest molecules with quantum chemical predictions. In the calculations, the non-polar environmental effect produced by the a-CD cavity on the C-13 shifts of included guest molecule has been formulated by the so-called solvent effect theory. The geometries of the complexes predicted theoretically were consistent with those... 

Empirical quantum-chemical predictions summarized above from classic inorganic chemistry and ligand field theory are correlated wifli macroscopic enhancements in the glass-transition temperature for Ni(II) complexes wifli poly(4-vinylpyridine). The 102°C enhancement in Tg of P4VP occurs when flie metal/pyridine-ligand concentration ratio is approximately 1 2 on a molar basis. It is postulated that thermal... 

Persson P, Lunell S, OJamae L (2002) Quantum chemical prediction of the adsorption conformations and dynamics at HCOOH-covered ZnO(lOlO) surfaces. Int J Quantum Chem 89(3) 172-180... 

Woon DE, Herbst E (2009) Quantum chemical predictions of the properties of known and postulated neutral interstellar molecules. Astrophys J Suppl Ser 185 273-288... 

Centrifugal Distortion and Vibration-Rotation Interactions Hyperfine Interactions Selection Rules and Intensity of Transitions Quantum Chemical Prediction of Rotational Spectra... 

We have shown that an interplay between quantum chemical predictions and experimental findings on optical response may offer complete information about structural and electronic properties of small metallic and mixed nonstoichiometric clusters as functions of their size and shape. Characteristic features of the studied systems are not smooth functions of their size. In other words, the properties of a small cluster with a given number of atoms can completely change by addition of a single atom. Cluster research is a field of... 

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