Small system fluctuations
Macroscopic thermodynamics, which refers to a large number of small systems, deals with strictly defined thermodynamic functions [1-3]. The current trend, consisting in the transfer of the thermodynamic approach to smaller particles, is connected with the hope of preserving the same thermodynamic functions and their interrelations in a wide range of system sizes. The question of the possibility of such an extension of the domain of the thermodynamic description remains open. To solve it, it is necessary to use the methods of statistical thermodynamics. With a decrease in the volume of the system, equilibrium fluctuations increase for all the thermodynamic characteristics [1,4]. The existence of fluctuations is a direct consequence of the discreteness of the structure of matter at the atomic-molecular level of any system and the thermal motion of molecules [5-7].