Host and adsorbate dynamics in silicates with flexible frameworks: Empirical force field simulation of water in silicalite

Patrice Bordat, Pierre Andŕ Cazade, Isabelle Baraille, Ross Brown

Research output: Contribution to journalArticlepeer-review

Abstract

Molecular dynamics simulations are performed on the pure silica zeolite silicalite (MFI framework code), maintaining via a new force field both framework flexibility and realistic account of electrostatic interactions with adsorbed water. The force field is similar to the well-known "BKS" model [B. W. H. van Beest, Phys. Rev. Lett. 64, 1955 (1990)], but with reduced partial atomic charges and reoptimized covalent bond potential wells. The present force field reproduces the monoclinic to orthorhombic transition of silicalite. The force field correctly represents the hydrophobicity of pure silica silicalite, both the adsorption energy, and the molecular diffusion constants of water. Two types of adsorption, specific and weak unspecific, are predicted on the channel walls and at the channel intersection. We discuss molecular diffusion of water in silicalite, deducing a barrier to crossing between the straight and the zigzag channels. Analysis of the thermal motion shows that at room temperature, framework oxygen atoms incurring into the zeolite channels significantly influence the dynamics of adsorbed water.

Original languageEnglish
Article number094501
JournalJournal of Chemical Physics
Volume132
Issue number9
DOIs
Publication statusPublished - 2010
Externally publishedYes

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