“…The effective masses are hence sensitive not only to the characteristics of the substances analysed, but also to external conditions, namely external pressure. The extreme increase in temperature can additionally cause the dissociation of molecules and ionisation, and leads to the transformation of matter to a plasma state, with possible intermediate condensed phases such as the condensed Rydberg matter, the rheological behaviour of which is unknown [59][60][61][62], although these can be of practical use to validate the TB approach to viscosity and its modification, applying the above concept of effective masses. Finally, we note that the Eyring-Kaptay (EK) equation used here to find the temperature T vm was extended from the temperature range, where its correctness was confirmed by the experiment [6,63], to the range where its validity may be questionable; therefore, Equation ( 3) is an approximate assessment of the crossover temperature T vm .…”