Local structural fluctuations and defects in metallic glasses

The atomic short range order in liquid and amorphous metals is most often described by the atomic pair distribution function. However, the local variation in properties and the structural defects are better described in terms of more collective structural parameters. It is suggested that the concept of the local structure including all the nearest neighbors provides the most useful description of the local short range order. In particular the method based upon the atomic-level stresses is able to describe satisfactorily the glass transition, structural relaxation and defects. The theory incorporates the free volume as one of the thermal defects, while other types of thermal defects also exist. Furthermore the feasibility of the existence of extended athermal defects is discussed.