Non-equilibrium atomic dynamics in solids

Atoms, molecules, electrons and impurities in solids are subjected to short-lived large energy fluctuations (SLEFs) arising from the background phonon-sea due to anharmonic interactions, These SLEFs arise from the 10-100 atoms situated within a few nanometer size volume surrounding the affected entity and have lifetimes of the order of a few picoseconds. The resulting dynamics is not in equilibrium with the remaining system over these space and time intervals; it results in unusual and fast atomic/cluster displacements and electronic transitions. The study of this 'fluctuations dynamics' has led to understanding 'abnormal' diffusion, desorption, chemical kinetics, ionic conductivity, etc. in solids especially in situations when the associated Arrhenius parameters are beyond the realm of conventional rate theory, This article reviews (a) advances made by the SLEF theory with a few examples drawn from literature and (b) results from computer experiments that reveal the microscopic nature of the fluctuations.