Although it is generally known that size effects can exist for thermodynamic properties like the internal energy and heat capacity until now these effects have usually been neglected,as no simplified procedure for calculating such effects has ene presented in the past.This paper presents an approach for estimating the size effects on the thermodynamic properties of thin films,which becomes especially prominent at cryogenic temperatures because of their dependence on the Planck distribution function.A size effect on the Deby temperature of thinfilms was previously observed,but the present analysis indicates that the Debye temperature is independent of the size of the specimen.A novel nondimensional parameter is also introduced that accurately describes the thermal behavior of thin films of different materials,and provides a clear demarsation between the microscopic and the macroscopic regimesfor the thermodynamic properties.With this nondimensional parameter,the heat capacity for a thin film of any given thickness and any material can be easily calculated,provided the bulk heat capacity of the material is known at the temperature of interest.
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