Molecular dynamics studies of nanoconfined water in clinoptilolite and heulandite zeolites.
The complete periodic series of alkali and alkaline earth cation variants (Li(+), Na(+), K(+), Rb(+), Cs(+), Mg(2+), Ca(2+), Sr(2+), and Ba(2+)) of clinoptilolite (Si : Al=5) and heulandite (Si : Al=3.5) aluminosilicate zeolites are examined by large-scale molecular dynamics utilizing a flexible SPC water and aluminosilicate force field. Calculated hydration enthalpies, radial distribution functions, and ion coordination environments are used to describe the energetic and structural components of extra-framework species while power spectra are used to examine the intermolecular dynamics. These data are correlated to evaluate the impact of ion-zeolite, ion-water, and water-zeolite interactions on the behavior of nanoconfined water. Analysis of the correlated data clearly indicates that the charge density of extra-framework cations appears to have the greatest influence on librational motions, while the anionic charge of the framework (i.e. Si:Al ratios) has a lesser impact.
Ockwig
Nathan W
NW
Geochemistry Department, Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185, USA. nockwig@sandia.gov
Cygan
Randall T
RT
Criscenti
Louise J
LJ
Nenoff
Tina M
TM
D003198:Computer Simulation; D008672:Metals, Alkali / Q000737:chemistry; D008673:Metals, Alkaline Earth / Q000737:chemistry; D008956:Models, Chemical; D014867:Water / Q000737:chemistry*; D017641:Zeolites / Q000737:chemistry*
D008672:Metals, Alkali; D008673:Metals, Alkaline Earth; D014867:Water; D017641:Zeolites