1.1.1. Fundamental Temperature

As a first step, we introduced the use of the scale of fundamental temperature, i.e., thermal excitation energy scale, *T*f, and its version normalized to the melting point of ice, *T*fn. By definition, *<sup>T</sup>*<sup>f</sup> <sup>=</sup> *<sup>k</sup>*B*T*, in which *<sup>k</sup>*<sup>B</sup> = 1.381·10−<sup>16</sup> erg/K (*k*<sup>B</sup> = 1.381·10−<sup>23</sup> J/K) is the Boltzmann constant, and *<sup>T</sup>* is the absolute temperature in K. We can also use the equation of *T*<sup>f</sup> = *RT*, in which *R* = 8.317 J/mol·K, the universal gas constant. If we need a dimensionless scale, it is expedient to use the normalized fundamental temperature scale, *T*fn, nor malized to the melting temperature of bulk water formally as *T*fn = *k*B·*T*/(*k*<sup>B</sup> × 273.15) = *T*/273.15. This way, it becomes possible to characterize the events of the beginning of molecular motion on an energy scale.
