An algorithm is proposed for the structural optimization of periodic systems in internal (chemical) coordinates. Internal coordinates may include in addition to the usual bond lengths, bond angles, out-of-plane and dihedral angles, various "lattice internal coordinates" such as cell edge lengths, cell angles, cell volume, etc. The coordinate transformations between Cartesian (or fractional) and...

Oxygen activation is a key step in the selective catalytic reduction of nitrogen oxides with ammonia (NH3-SCR) over Cu-chabazite. We present direct measurements oxygen adsorption at low temperatures [NH3?Cu?NH3]+ complexes and framework-bound Cu+ species Cu-chabazite Si/Al=14 using isothermal microcalorimetry combined mass spectrometry. The enthalpy change for O2 200 °C determined to be ?79 kJ/...

Gas separation efficiencies of three zeolite membranes (Faujasite, MFI, and Chabazite) have been examined using the method of molecular dynamics. Our investigation has allowed us to study the effects of pore size and structure, state conditions, and compositions on the permeation of two binary gas mixtures, O(2)N(2) and CO(2)N(2). We have found that for the mixture components with similar sizes...

A new zeolite, COK-24, which is an intergrowth of erionite (ERI) and chabazite (CHA), was successfully synthesized for the first time. This realized via a mixed gel approach. The formation a...

A new locality of zeolite minerals occurs on the NE edge Jedlka village, at SE slope Hlídka hill, 2 km to W Benešov nad Ploučnicí (northern Bohemia, Czech Republic). The mineralization is developed in Cenozoic analcime-nepheline tephrite. Ten mineral species (gmelinite-K, analcime, harmotome, chabazite-Ca, lévyne-Ca, mezolite, natrolite, offretite, phillipsite-K, thomsonite-Ca) were found small...

The differences in valence and size between extra-framework cations exert a significant effect on the nitrogen sorption ability synthesised chabazite zeolites (K-CHA, Cs-CHA, Ca-CHA, Ba-CHA, Sr-CHA Zn-CHA).

A composite material was prepared using chitosan and chabazite for the removal of Eriochrome T black dye from water. Scanning electron microscopy (SEM) analyses showed particles embedded in matrix. Thermogravimetric indicated that degrades chemically at temperatures above 225 °C; only experiences weight decrease due to moisture loss. Fourier transform infrared spectroscopy (FTIR) on detected pr...