Zeolites, computational chemistry

Sauer, J., 1998, Zeolites Applications of Computational Methods in Encyclopedia of Computational Chemistry, Schleyer, P. v. R. (Editor-in-Chief), Wiley, Chichester. 

There has been a phenomenal growth of interest in theoretical simulations over the past decade. The concomitant advances made in computing power and software development have changed the way that computational chemistry research is undertaken. No longer is it the exclusive realm of specialized theoreticians and supercomputers rather, computational chemistry is now accessible via user-friendly programs on moderately priced workstations. State-of-the-art calculations on the fastest, massively parallel machines are continually enlarging the scope of what is possible with these methods. These reasons, coupled with the continuing importance of solid acid catalysis within the world s petrochemical and petroleum industries, make it timely to review recent work on the theoretical study of zeolite catalysis. 

Framework Dynamics Including Computer Simulations of the Water Adsorption Isotherm of Zeolite Na-MAP. See also J.-R. Hill, C. M. Freeman, and L. Subramanian, in Reviews in Computational Chemistry, K. B. Lipkowitz and D. B. Boyd, Eds., Wiley-VCH, New York, 2000, Vol. 16, pp. 141-216. Use of Force Fields in Materials Modeling. The shell model is also discussed by B. van de Graaf, S. L. Njo, and K. S. Smirnov, in Reviews in... 

Chapter 7. Computational Approaches in Zeolite Structural Chemistry... 

The reliability of method for electronic structure calculations and models used in zeolite modeling is briefly reviewed. Only traditional ab initio methods and methods based on the density functional theory are discussed. Periodic, cluster, and combined models are described and their suitability for investigation of various properties is discussed. This contribution is written for non-experts in computational chemistry. The author hopes that it will help them to gain a basic orientation in the field. 

Computational techniques in general arc used in various areas of zeolite research. In fact, just such a basic question as what is the structure of a zeolite relies on the zeolite modeling. Currently, the methods of computational chemistry are used in investigation of almost any property of zeolites, including, e. g., zeolite structures, zeolite characterizations (modeling, e. g., the UV-vis, IR, NMR, or ESR spectra), and catalytic activities. 

Van der Graaf B, S L Njo and K S Smirnov 2000. Introduction to Zeolite Modeling In Lipkowitz K B and D B Boyd (Editors) Reviews in Computational Chemistry Volume 14 New York, VCH Publishers, pp. 137-223... 

Nevins N, K Chen and N L Allinger 1996c Molecular Mechamcs (MM4) Vibrational Frequency Calculations for Alkenes and Conjugated Hydrocarbons. Journal of Computational Chemistry 17 730-746 Nicholas J B, A J Hopfmger, F R Trouw and L E Iton 1991 Molecular Modelling of Zeolite Structure. 2. Structure and Dynamics of Silica Sodalite and Silicate Force Field. The Journal of the American Chemical Society 113.4792-4800. 

Van de Graaf B, Njo SL, Smirnov KS (2000) Introduction to zeolite modeling. In Lipkowitz KB, Boyd DB (eds) Reviews in computational chemistry. Vol 14, Wiley-VCH Publishers, New York, p 137... 

Rouvray DH (1997) Do molecular models accurately reflect reahty Chemind 15 587-590 Rouvray DH (1995) John Dalton The world s first stereochemist. Endeavour 19 52-57 Schleyer PVR (1998) Encyclopedia of Computational Chemistry. John Wiley and Sons, New York Shen DM, Jale SR, Bulow M, Ojo AF (1999) Sorption thermodynamics of nitrogen and oxygen on CaA zeolite. Stud Surf Sci Catal 125 667-674... 

A class of porous alumino-sihcate materials called zeolites has been known for almost 300 years. They are best known for their role as catalysts. In chapter four, Marcel AUavena and David White present a review of applications of computational chemistry to the proton transfer, primary process for acid-base chemistry on zeolites. Recent ab initio results are compared to experimental studies and critically reviewed. Future directions of the field are given, and the importance of the Car-Parrinello method in exploring the dynamic aspects of reactivity in zeolites is discussed. 

Schleyer, P. V. R. 1998. Encyclopedia of Computational Chemistry, John WUey Sons, Chichester, UK. Schroder, K. R, Sauer, J., Leslie, M., and Catlow, C. R. A. 1992. Bridging hydroxyl groups in zeolitic catalysts A computer simulation of their structure, vibrational properties and acidity in protonated faujasites (H-Y... 

For molecules in the gas phase these are questions for which quantum chemical ab initio methods provide answers with about the same accuracy as experiments. For crystals like zeolites with up to hundreds of atoms in the unit cell, the same type of question is a real challenge for computational chemistry in general and ab initio quantum chemistry in particular. Compared to other very large systems such as liquids, molecules in solution, or biomolecules, zeolites have the advantage of a regular and well-defined structure yet with a broad variety. Hence, the methods developed for zeolite catalysts and the experience gained when applying them can be exploited in studies on other, even more complex, systems, for example enzymes. 

The computational chemistry toolbox [5] includes a wide variety of methods useful for the description of different physical and chemical processes in zeolites. They are usually classified on the basis of the size of the chemical system that they can simulate and the... 

Computational studies on catalysis by zeolites begin with the need to identify the structures of the most probable active sites as well as different species formed within the zeolite pores in the course of the reaction. Such species correspond to specific stationary points on a so-called potential energy surface (PES) that is one of the core concepts in computational chemistry. The first derivative of the potential energy at these points is zero with respect to every degree of freedom in the system. 

The exceptional catalytic properties and structural features of zeolites are a powerful stimulus for both experimental and theoretical research. With the advent of the computer age and with the spectacular development of advanced quantum chemical computational methods in the last decade, one may expect that molecular quantum theory will find more and more practical and even industrial applications. The most rapid progress is expected to occur along the borderline of traditional experimental and theoretical chemistry, where experimental and computational (theoretical) methods can be combined in an efficient manner to solve a variety... 

In the following we shall briefly review some of the recent applications of computational quantum chemistry to zeolites, in particular, some studies on the quantum chemical origin of Loewenstein s aluminum avoidance rule, and on the role of counter ions in stabilizing various structural units in zeolite lattices. These calculations are often extremely time consuming, nevertheless, the scope of their application is continuously expanding. 

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