Crystal structures and thermodynamic properties of phase change materials (1-CnH2n+1NH3)2CdCl4(s) (n = 15 and 16)

Two novel crystalline compounds (1-C15H31NH3)2CdCl4(s) and (1-C16H33NH3)2CdCl4(s), which may be used as the solid–solid phase change materials, were synthesized. X-ray crystallography was applied to characterize crystal structures of the two compounds. Both of them are monoclinic, the space group is both C2/c, and Z = 4. Lattice potential energies (UPOT) of the title compounds were calculated to be 832.31 kJ mol−1 for (1-C15H31NH3)2CdCl4(s) and 814.26 kJ mol−1 for (1-C16H33NH3)2CdCl4(s). Low-temperature heat capacities of the two compounds were measured by a precise automatic adiabatic calorimeter in the temperature range from 78 to 395 K. The temperatures, molar enthalpies and entropies of two phase transitions for each of the two compounds were determined. The smoothed heat capacities and thermodynamic functions of the two compounds relative to the standard reference temperature 298.15 K were calculated and tabulated at 5 K intervals based on experimental heat capacities.