Crystallographically identified cation

Table II. Crystallographically identified cation sites and populations for K-A. The numbers in this table refer to the number of cations per pseudo-unit cell. Deh. is dehydrated, and Hyd. is hydrated. The last entry in the Table is for a. .Na A sample...

The shape selectivity of zeolites is influenced by the location and distribution of charge-compensating cations. The charge-compensating ions other than protons are all quadrupolar. and Li NMR spectra of dehydrated LiX-1.0 identified three crystallographically distinct sites [221]. In the case NaX with Si/Al ratio of 1.23, six distinct sodium sites were identified using fast Na NMR, DOR and nutation techniques [222]. Na MQMAS has been extensively studied for zeolites X and Y [155]. Other cations like Cs and La in zeolites have also been investigated [155,... 

To correlate the adsorption and diffusion properties to the cation distribution in the structure of CaNaA zeolites, temperature programmed desorption, anomalous X-ray powder diffraction and quasi elastic neutron scattering experiments were performed. It is shown that water adsorption and diffusion behaviour differs with the calcium content. Fourier maps obtained from anomalous diffraction experiments near the Ca K-edge allow to identify the calcium crystallographic sites unambiguously. 

Sodium valproate is a pharmaceutical with applications in the treatment of epilepsy, bipolar disorder, and other ailments. It can exist in many hydrated and acid-stabilized forms in the solid state. Solid-state and Na NMR study of several forms of sodium valproate have been presented. Na MAS, DOR, and MQMAS NMR spectra are shown to provide useful information on the number of molecules in the asymmetric unit, the local coordination geometry of the sodium cations, and the presence of amorphous phases. TNvo previously identified forms are shown to be highly similar, or identical, according to the Na NMR data. The utility of carrying out both DOR and MQMAS NMR experiments to identify all crystallographically unique sites is demonstrated. CP MAS NMR spectra also provide complementary information on... 

---