The glass transition is described as a time-and history-independent singular event, which takes place in an interval dependent on the distribution width of the molecular vibration amplitudes. Free volume is redefined and its generation is the result of the fluctuating transfer of thermal energy into the condensed matter and the resulting combined interactions between the vibration elements. This creates openings between the elements which are larger than the cross-section of an adjacent element

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... or parts thereof. Possible shifts of molecules or molecular parts through such gaps depend on the size and axis orientation and do not require further energetic activation. After a displacement additional volume is created by delays in occupying abandoned positions and restoring the energetic equilibrium. The different possibilities of axis orientation in space result in different diffusive behavior of simple molecules and chain molecules, silicate network formers and associating liquids. Glass transformation takes place at a critical volume Vg 0 when the cross-section of the apertures becomes smaller than the cross-section of the smallest molecular parts. The glass transition temperature Tg 0 is assigned to Vg 0 and is therefore independent of molecular relaxation processes. Tg 0 is well above the Kauzmann and Vogel temperatures, usually just a few degrees below the conventionally measured glass temperature Tg (qT). The specific volume at the two temperatures mentioned above cannot be achieved by a glass with an unordered structure but only with aligned molecular axes, i. e. in the crystalline state. Simple liquids consisting of non-spherical molecules additionally alter their behavior above Vg 0 at Vg l where the biggest gaps are as small as the largest molecular diameter. Tg l is located in the region of the crystalline melting point Tm. Both regions, above and below Tm, belong to different physical states and have to be treated separately. In the region close to Vg 0 resp. Tg 0 the distribution of vibration amplitudes has to be taken into account. The evolution of transport properties depend on specific volume and not on temperature per se. The boundary volume Vg 0 in conjunction with the distribution width of the molecular vibrations when approaching Vg 0 is the key to understanding the glass transition.