Combined Quantum Mechanics:  Interatomic Potential Function Investigation of rac-meso Configurational Stability and Rotational Transition in Zirconocene-Based Ziegler−Natta Catalysts

2000 ◽  
Vol 104 (46) ◽  
pp. 10932-10938 ◽  
Author(s):  
Amitesh Maiti ◽  
Marek Sierka ◽  
Jan Andzelm ◽  
Joe Golab ◽  
Joachim Sauer
Keyword(s):  
Quantum Mechanics ◽  
Potential Function ◽  
Interatomic Potential ◽  
Rotational Transition ◽  
Configurational Stability ◽  
Ziegler Natta Catalysts

Coordination and siting of Cu+ ions in ZSM-5: A combined quantum mechanics/interatomic potential function study

1999 ◽  
Vol 1 (8) ◽  
pp. 2019-2026 ◽  
Author(s):  
Dana Nachtigallová ◽  
Petr Nachtigall ◽  
Marek Sierka ◽  
Joachim Sauer
Keyword(s):  
Quantum Mechanics ◽  
Potential Function ◽  
Interatomic Potential ◽  
Function Study ◽  
Cu Ions

Comparing the Acidities of Microporous Aluminosilicate and Silico-Aluminophosphate Catalysts: A Combined Quantum Mechanics-Interatomic Potential Function Study

1998 ◽  
Vol 63 (9) ◽  
pp. 1394-1408 ◽  
Author(s):  
Joachim Sauer ◽  
Klaus-Peter Schröder ◽  
Volker Termath
Keyword(s):  
Quantum Mechanics ◽  
Potential Function ◽  
Interatomic Potential ◽  
Lattice Energy ◽  
Model Potential ◽  
Acid Sites ◽  
Basis Sets ◽  
Intermolecular Potential ◽  
Average Error ◽  
Maximum Deviation

DFT-B3LYP calculations are performed on 4-ring models of aluminophosphates (AlPOs) and silico-aluminophosphates (SAPOs). The results are used to fit the parameters of ion pair shell model potential functions. The potentials obtained are tested in lattice energy minimizations for berlinite and the microporous materials AlPO-18, AlPO-40, AlPO-52, and VPI-5. Not only does the potential reproduce the observed structures (average error of the cell constants 1.3%), it also predicts vibrational frequencies over the whole frequency range equally well (maximum deviation 50 cm-1). The potential is used to predict the structures and properties of Bronsted acid sites in an aluminosilicate and a SAPO with the chabazite framework structure (HSSZ-13 and HSAPO-34). A new combined quantum mechanics-intermolecular potential function approach (QM-Pot) is used at the DFT level. Comparison is made with full periodic DFT calculations using plane wave basis sets. The deprotonation energies corrected for systematic errors of the methods used are 1 231-1 235 and 1 261-1 280 kJ/mol for HSSZ-13 and HSAPO-34, respectively. The same acid site has a lower acidity in a SAPO than in an aluminosilicate zeolite of the same structure.

A Computational Study of the Translational Motion of Protons in Zeolite H-ZSM-5

2000 ◽  
Vol 658 ◽  
Author(s):  
M.E. Franke ◽  
M. Sierka ◽  
J. Sauer ◽  
U. Simon
Keyword(s):  
Activation Energy ◽  
Quantum Mechanics ◽  
Potential Energy ◽  
Interatomic Potential ◽  
Computational Study ◽  
Translational Motion ◽  
Energy Profile ◽  
Potential Energy Profile ◽  
Transition Structures ◽  
Deprotonation Energy

ABSTRACTThe potential energy profile for proton translational motions between two neighboring Alsites in zeolite H-ZSM-5 is calculated by a combined quantum mechanics-interatomic potential function approach. Thepotential energies of the six stable intermediate proton positions and the five transition structures along this path show an almost symmetrical trend reaching the maximum in the middle between these sites. Therefore, the maximum barrier will decrease with decreasing SiO2/Al2O3 ratio of thezeolite. For the SiO2/Al2O3 ratio examined (190) an activation energy of∼ 210 kJ/mol is calculated. This is much lower than the energy of deprotonation, about 1300 kJ/mol. The deprotonation energy of an Al-OH-Si bridge is obviously partially compensated by the proton affinity of the Si-O-Si bridges.

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