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Title: Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel's salt)

Abstract

The dynamical behavior of Cl{sup {minus}} and H{sub 2}O molecules in the interlayer and on the (001) surface of the Ca-aluminate hydrate hydrocalumite (Friedel's salt) over a range of temperatures from {minus}100 to 300 C is studied using the technique of isothermal-isobaric molecular dynamics computer simulations. This phase is currently the best available model compound for other, typically more disordered, mixed-metal layered hydroxides. The computed crystallographic parameters and density are in good agreement with available X-ray diffraction data and the force field developed for these simulations preserves the structure and density to within less than 2% of their measured values. In contrast to the highly ordered arrangement of the interlayer water molecules interpreted from the X-ray data, the simulations reveal significant dynamic disorder in water orientations. At all simulated temperatures, the interlayer water molecules undergo rapid librations (hindered hopping rotations) around an axis essentially perpendicular to the layers. This results in breaking and reformation of hydrogen bonds with the neighboring Cl{sup {minus}} anions and in a time-averaged nearly uniaxial symmetry at Cl{sup {minus}}, in good agreement with recent {sup 35}Cl NMR measurements. Power spectra of translational, vibrational, and vibrational motions of interlayer and surface Cl{sup {minus}} and H{sub 2}O weremore » calculated as Fourier transforms of the atomic velocity autocorrelation functions and compared with the corresponding spectra and dynamics for a bulk aqueous solution. The ordered interlayer space has significant effects on the motions. Strong electrostatic attraction between interlayer water molecules and Ca atoms in the principal layer makes the Ca{hor_ellipsis}OH{sub 2} bond direction the preferred axis for interlayer water librations. The calculated diffusion coefficient of Cl{sup {minus}} as an outer-sphere surface complex is almost three times that of inner-sphere Cl{sup {minus}}, but is still about an order of magnitude less than that of Cl{sup {minus}} in bulk aqueous solution at the same temperature.« less

Authors:
; ;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
751356
Report Number(s):
SAND2000-0457J
TRN: AH200019%%58
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Journal Article
Journal Name:
American Mineralogist
Additional Journal Information:
Other Information: Submitted to American Mineralogist; PBD: 17 Jan 2000
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CALCIUM COMPOUNDS; ALUMINATES; HYDROXIDES; SURFACE PROPERTIES; CHLORIDES; WATER; MICROSTRUCTURE; ELECTRONIC STRUCTURE; AQUEOUS SOLUTIONS

Citation Formats

KALINICHEV, ANDREY G, KIRKPATRICK, R JAMES, and CYGAN, RANDALL T. Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel's salt). United States: N. p., 2000. Web. doi:10.2138/am-2000-0720.
KALINICHEV, ANDREY G, KIRKPATRICK, R JAMES, & CYGAN, RANDALL T. Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel's salt). United States. doi:10.2138/am-2000-0720.
KALINICHEV, ANDREY G, KIRKPATRICK, R JAMES, and CYGAN, RANDALL T. Mon . "Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel's salt)". United States. doi:10.2138/am-2000-0720. https://www.osti.gov/servlets/purl/751356.
@article{osti_751356,
title = {Molecular modeling of the structure and dynamics of the interlayer and surface species of mixed-metal layered hydroxides: Chloride and water in hydrocalumite (Friedel's salt)},
author = {KALINICHEV, ANDREY G and KIRKPATRICK, R JAMES and CYGAN, RANDALL T},
abstractNote = {The dynamical behavior of Cl{sup {minus}} and H{sub 2}O molecules in the interlayer and on the (001) surface of the Ca-aluminate hydrate hydrocalumite (Friedel's salt) over a range of temperatures from {minus}100 to 300 C is studied using the technique of isothermal-isobaric molecular dynamics computer simulations. This phase is currently the best available model compound for other, typically more disordered, mixed-metal layered hydroxides. The computed crystallographic parameters and density are in good agreement with available X-ray diffraction data and the force field developed for these simulations preserves the structure and density to within less than 2% of their measured values. In contrast to the highly ordered arrangement of the interlayer water molecules interpreted from the X-ray data, the simulations reveal significant dynamic disorder in water orientations. At all simulated temperatures, the interlayer water molecules undergo rapid librations (hindered hopping rotations) around an axis essentially perpendicular to the layers. This results in breaking and reformation of hydrogen bonds with the neighboring Cl{sup {minus}} anions and in a time-averaged nearly uniaxial symmetry at Cl{sup {minus}}, in good agreement with recent {sup 35}Cl NMR measurements. Power spectra of translational, vibrational, and vibrational motions of interlayer and surface Cl{sup {minus}} and H{sub 2}O were calculated as Fourier transforms of the atomic velocity autocorrelation functions and compared with the corresponding spectra and dynamics for a bulk aqueous solution. The ordered interlayer space has significant effects on the motions. Strong electrostatic attraction between interlayer water molecules and Ca atoms in the principal layer makes the Ca{hor_ellipsis}OH{sub 2} bond direction the preferred axis for interlayer water librations. The calculated diffusion coefficient of Cl{sup {minus}} as an outer-sphere surface complex is almost three times that of inner-sphere Cl{sup {minus}}, but is still about an order of magnitude less than that of Cl{sup {minus}} in bulk aqueous solution at the same temperature.},
doi = {10.2138/am-2000-0720},
journal = {American Mineralogist},
number = ,
volume = ,
place = {United States},
year = {2000},
month = {1}
}