The low temperature heat capacity of thallous bromide

Measurements of the specific heat of TlBr between 5 and 290 K are reported. These are believed to be accurate in an absolute sense to within 1% at 290 K, falling to 5% at 5 K. The Gruneisen parameter has been calculated as a function of temperature between 290 and 30 K, and at T=0. In spite of a similarity of gamma infinity and gamma 0 between 2 and 3, a marked variation of gamma with temperature independence of gamma in caesium halides. Thermodynamic analysis reveals features of a frequency spectrum which accord qualitatively with the concept given by an application of the shell model. The quasiharmonic approximation has been applied to the calculation of the maximum frequencies nu D (n) of the Debye distributions having the same nth moments as the spectrum in the real crystal for -3<or=n<or=6.