Аннотация:We develop the notion that amorphous substances undergo reversible configurational structural changes
accompanied by local expansion and compression (atom delocalization) near the glass transition temperature. They are similar in nature to configurational changes in the structure of glasses in the case of reversible frozen (plastic) deformation and its thermally stimulated relaxation. We assume that the glass-liquid transition is associated with the process of atom delocalization caused by bond breaking and formation of elementary excitations e.g. configurons. We discuss the possibility of detection of configuron formation and atom delocalization near glass transition based on temperature dependence of X-rays or neutron first sharp diffraction (pair distribution function) minimum.