Quantum mechanical calculations on molecular sieves. 2. Model cluster investigation of silicoaluminophosphates

• Published in: Journal of physical chemistry (1952) Vol. 94; no. 4; pp. 1687 - 1692
• Main Authors: Derouane, Eric G, Fripiat, J. G, Von Ballmoos, R
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.02.1990
• Subjects: 360603 > Materials > Properties; ADSORBENTS; CALCULATION METHODS; CATALYSTS; DATA; DATA ANALYSIS; INFORMATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; MATERIALS SCIENCE; MATHEMATICAL MODELS; MECHANICS; MOLECULAR SIEVES; NUMERICAL DATA; OXYGEN COMPOUNDS; PHOSPHATES; PHOSPHORUS COMPOUNDS; QUANTUM MECHANICS; SILICATES; SILICON COMPOUNDS 400201 > Chemical & Physicochemical Properties; STABILITY; THEORETICAL DATA
• ISSN: 0022-3654; 1541-5740
• DOI: 10.1021/j100367a085

Ab initio molecular orbital calculations have been performed on model clusters simulating silicate, aluminosilicate, and silicoaluminophosphate dimeric and trimeric entities. This investigation was aimed at obtaining preliminary information on the relative stability of the Si-O-Al, Si-O-P, and Al-O-P bridges and on modifications generated by the presence of phosphorus in such and related systems. The results show that the Al-O-P bridge is more stable than Si-O-Al or Si-O-P linkages, which is in agreement with the high stability of framework aluminum phosphate structures. The results also suggest that bridging hydroxyl groups in aluminum phosphates-the proton originating from nonstoichiometry, defects, or Si incorporation-should show acidic properties.