The Chirality of SiO4 in Materials – David Avnir

Date: Wed. February 11th, 2015, 12:30 pm-1:30 pm
Location: Rockefeller 221

SiO4 is a common building block of many materials, both crystalline such as quartz, silicates and zeolites, and amorphous, such as silica. Although intuitively one would think that SiO4 is an achiral perfect tetrahedron, in the vast majority of silicon-oxide based materials, that tetrahedron is of lower symmetry, to the degree of being chiral. Discussion of the chirality of SiO4 and its manifestation in crystalline and amorphous materials, will be the main focus of this lecture. Specific topics to be covered include the induction of chirality in silicas; the contribution of randomness to the emergence of chirality; the chirality of zeolites and silicates; methods for evaluating the degree of chirality of the SiO4 unit; methods for attachment of a handedness label (left or right) to that unit, and more. The lower-than-tetrahedral symmetries of the SiO4 unit will be presented and discussed. Correlations chirality content and physical measurables, will be presented.