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 atom s situated within a few nanometer size volume surrounding the affected enti ty and have lifetimes of the order of a few picoseconds. The resulting dyna mics is not in equilibrium with the remaining system over these space and t ime intervals; it results in unusual and fast atomic/cluster displacements and electronic transitions. The study of this 'fluctuations dynamics' has l ed to understanding 'abnormal' diffusion, desorption, chemical kinetics, io nic conductivity, etc. in solids especially in situations when the associat ed Arrhenius parameters are beyond the realm of conventional rate theory, T his article reviews (a) advances made by the SLEF theory with a few example s drawn from literature and (b) results from computer experiments that reve al the microscopic nature of the fluctuations.