Ab initio periodic Hartree-Fock investigation of a zeolite acid site

Journal Article · Wed Jun 15 00:00:00 EDT 1994 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00091a055· OSTI ID:7166634

Nicholas, J B; Hess, A C ^[1]

---

1. Pacific Northwest Lab., Richland, WA (United States)

We have studied theoretical models of a zeolite Bronsted acid site using ab initio periodic Hartree-Fock (PHF) theory. We present results for both one and two acid sites inside a sodalite structure ([beta]-cage). We optimized the geometry of the bridging hydroxyl groups using the STO-3G basis set. All other reported crystal properties were evaluated using the more complete 6-21G (in which the outermost orbital exponents were reoptimized for the solid) level of theory. The results of the periodic calculations are compared to available experimental data, similar periodic calculations of silica sodalite in which there are no acid sites, and calculations of clusters that mimic parts of the periodic structure. The optimized geometry of the single bridging hydroxyl group has internal coordinates of Si-O = 1.64 [angstrom], Al-O = 1.72 [angstrom], O-H = 0.97 [angstrom], Si-O(H)-Al = 136.3[degree], and Si-O-H = 110.7[degree], and the hydrogen is bent 25.2[degrees] out of the Si-O-Al plane. The optimized geometry of the bridging hydroxyl group in the two-acid site model is very similar, with Si-O = 1.65 [angstrom], Al-O = 1.72 [angstrom], O-H = 0.97 [angstrom], Si-O(H)-Al = 135.5[degree], Si-O-H = 112.7[degree], and an out-of-plane angle of 21.5[degree]. 42 refs., 11 figs., 5 tabs.

• DOE Contract Number: AC06-76RL01830
• OSTI ID: 7166634
• Journal Information: Journal of the American Chemical Society; (United States), Vol. 116:12; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
CRYSTAL STRUCTURE
COMPUTERIZED SIMULATION
MATHEMATICAL MODELS
ZEOLITES
CHEMICAL BONDS
COMPILED DATA
ELECTROSTATICS
HARTREE-FOCK METHOD
CALCULATION METHODS
DATA
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
MINERALS
NUMERICAL DATA
SILICATE MINERALS
SIMULATION
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
400201 - Chemical & Physicochemical Properties
990200 - Mathematics & Computers