Structure Deformations and Existence of the α-β Transition in MXO4 Quartz-like Materials

Abstract The paramount importance of M - X interactions in determining the existence or nonexistence of an α-β transition can be shown by a general survey of all known or predicted quartz-like materials, MX O 4 . This distance, M - X , defined as the nonbonded radius sum, prescribes structure packing. If the M -O and X -O distances increase, interterahedron distortion will increase in relation to the decrease of the M -O- X angle, 0 , and decrease of the tilt angle, δ. From a structural point of view, a borderline value of δ ∼ 22° or θ ∼ 136° has been extrapolated for the existence of an α-β transition.