The effect of copper and alanine-copper impurities on the heat capacity of triglycine sulfate

The method of adiabatic calorimetry is used to study the temperature dependences of the monocrystals of triglycine sulfate, alloyed with the impurities $Cu^{2+}$ and $Cu^{2+}+L-\alpha$-alanine in the temperature range 240-350 K. The copper impurity causes an insignificant change (in comparison with the pure crystal) of the temperature dependences of the heat capacity in the region of the phase transition which, however, sharply increase for the copper-alanine impurity. The observed effects can be explained using the concept of displacement field inside the crystal.