Modeling local chemistry in the presence of collective phenomena.
Confinement within the nanoscale pores of a zeolite strongly modifies the behavior of small molecules. Typical of many such interesting and important problems, realistic modeling of this phenomena requires simultaneously capturing the detailed behavior of chemical bonds and the possibility of collective dynamics occurring in a complex unit cell (672 atoms in the case of Zeolite-4A). Classical simulations alone cannot reliably model the breaking and formation of chemical bonds, while quantum methods alone are incapable of treating the extended length and time scales characteristic of complex dynamics. We have developed a robust and efficient model in which a small region treated with the Kohn-Sham density functional theory is embedded within a larger system represented with classical potentials. This model has been applied in concert with first-principles electronic structure calculations and classical molecular dynamics and Monte Carlo simulations to study the behavior of water, ammonia, the hydroxide ion, and the ammonium ion in Zeolite-4a. Understanding this behavior is important to the predictive modeling of the aging of Zeolite-based desiccants. In particular, we have studied the absorption of these molecules, interactions between water and the ammonium ion, and reactions between the hydroxide ion and the zeolite cage. We have shown that interactions with the extended Zeolite cage strongly modifies these local chemical phenomena, and thereby we have proven out hypothesis that capturing both local chemistry and collective phenomena is essential to realistic modeling of this system. Based on our results, we have been able to identify two possible mechanisms for the aging of Zeolite-based desiccants.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 921743
- Report Number(s):
- SAND2005-0070; TRN: US200806%%24
- Country of Publication:
- United States
- Language:
- English
Similar Records
Challenges in Modeling Electrochemical Reaction Energetics with Polarizable Continuum Models
Challenges at the Frontiers of Matter and Energy: Transformative Opportunities for Discovery Science
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ZEOLITES
MATHEMATICAL MODELS
CHEMICAL BONDS
ENCAPSULATION
MOLECULES
DENSITY FUNCTIONAL METHOD
ELECTRONIC STRUCTURE
MOLECULAR DYNAMICS METHOD
MONTE CARLO METHOD
WATER
AMMONIA
HYDROXIDES
AGING
DESICCANTS
Cell membranes.
Chemical bonds-Mathematical models.
Chemical reactions-Mathematical models.