Origin Of Mixed Alkali Effect Research Articles

A Molecular Dynamics Investigation of the Structures and Mixed Alkali Effect in Sulfate Glasses

A molecular dynamics stimulation of alkali sulfate-zinc sulfate melts and glasses is presented. Oxygen coordinations of Zn2+, Na+, and K+ cations have been found to be nearly six, eight, and twelve respectively. The radial distribution function has been calculated and compared with the same reported from experimental X-ray diffraction work. Several important aspects of a modified random close packing model described earlier to account for the behavior of sulfate glasses have been confirmed by the present molecular dynamics simulation. Diffusion coefficients of various ions have been evaluated from mean squared displacement data and occurrence of the mixed alkali effect has been noted. A surprising spatial correlation of dissimilar alkali ions has been observed and it is suggested that it provides support for a structural origin of mixed alkali effect in ionic glasses.

Electrical conductivity studies in sulphate glasses and the mixed alkali effect

Electrical conductivities of alkali sulphate-zinc sulphate glasses have been measured. The variation of conductivity with compositon confirms the presence of the mixed alkali effect. The origin of mixed alkali effect has been explained on the basis of structural considerations reported earlier by us.

Ionic sulphate glasses

Sulphate glasses are typical ionic glasses in the sense they are constituted of discrete anions. In this review various physical properties of K2SO4, Na2SO4 and ZnSO4 glasses have been reported. A model of random close packing of ions has been suggested and used to interpret several properties including the origin of mixed alkali effect.