Author/Authors :
Schrِder، نويسنده , , F. and Winkler، نويسنده , , B. and Bauer، نويسنده , , J.D. and Haussühl، نويسنده , , E. and Rivera Escoto، نويسنده , , B. and Tristan Lَpez، نويسنده , , F. and Avalos Borja، نويسنده , , M. and Richter، نويسنده , , C. and Ferner، نويسنده , , J.، نويسنده ,
Abstract :
The low temperature heat capacities of single crystals of fully protonated acetylsalicylic acid, measured between 2 K < T < 80 K, have been compared to samples in which the methyl-group was replaced by CD3, CH2D and 13CH3. For the partially methyl-deuterated crystal (CH2D) a significant excess heat capacity was found below T < 40 K with a broad maximum around T ≈ 14 K. The thermodynamic data are explained on the basis of a Schottky model using results obtained in earlier NMR and neutron spectroscopic experiments. In contrast, the excess heat capacity of the fully deuterated compound can be explained by a change of the phonon density of states.
