Mathematical description of additional low temperature specific heat components for twofluoropolymers, PTFE and PCTFE

Our orthonormal polynomial expansion method (OPEM) is used here for describing the additional low temperature specific heat components of Polytetrafluoroethylen (PTFE) and Poly‐chlorotrifluoroethylene (PCTFE). The temperature dependencies of the excess specific heat for the both semi‐crystalline polymers are described mathematically up to 7–8 K in the present work. The peculiarity established earlier in Cp/T3 vs. T of the PTFE and PCTFE manifested by a maximum appearing around 5 K for both fluoroplasts is hardly to be explained with the Debye model. This hump analyzed in our previous work was related to the additional low‐frequency vibration modes (soft modes), localized together with lattice vibrations (sound waves) as it is postulated in the Soft Potential Model (SPM). The estimated excess specific heat data and approximating curves determined by the usual polynomial coefficients obtained by orthonormal ones in our OPEM approach, are presented too.