Dynamic processes in condensed matter

A large number of physical properties of crystals and amorphous or poorly crystallizable matter, i.e. of glasses, polymers and biopolymers, are of a dynamic or kinetic nature. Dynamic and kinetic are roughly distinguished by their time scales. In the first case we are dealing with atomic or molecular times, i.e. from about 10-14 to 7-10 sec, in the second with macroscopic times, from 6-10 sec to the range of hours. This large time scale spans a variety of phenomena: the shortest of these periods correspond approximately to the thermal oscillations of the atoms (phonons) in the structure of diamond or silicon; times around 9-10 sec are typical for the diffusion of atoms in crystals and for motion sequences in polymers and biopolymers.

Since the full range of the time scale is about 18 powers of ten, a single measurement method is not sufficient for experimental measurement. The short times are measured (in the range of 10-14 to 10-11 sec), with simultaneous spatial resolution, by energy shifts with neutron spectrometers (inelastic neutron scattering). Slower structural changes can be measured directly by stroboscopic methods. In processes in the range of one second, the change in the crystal structure can already be continuously monitored today.

The movement of atoms in solids and the chemical bonds between atoms depend on pressure and temperature. By changing these state variables, structural transformations can be induced from those mechanisms that can be deduced from diffraction experiments with neutrons and X-rays as well as from the abnormal behaviour of macroscopic properties. From this, a deeper understanding of the characteristic dynamics of interaction and processes in the atomic range can be obtained.