Local dynamics of YBa2Cu3O6+x and O(1)-defect dynamical stability.

Abstract

Using Green{close_quote}s functions of the simple shell model of YBa{sub 2}Cu{sub 3}O{sub 6+{ital x}}, the local dynamics of the chain-defect O(1) ion is investigated. An {approximately}30{percent} softening of the effective noncentral force constants leads to dynamical instability of this ion with the perpendicular shift out of the chain in the {ital a} direction of the crystal. {copyright} {ital 1996 The American Physical Society.}