Low-temperature heat capacity of α and γ polymorphs of glycine

Low-temperature heat capacity of two polymorphs of glycine (alpha and gamma) was measured from 5.5 to 304 K and thermodynamic functions were calculated. Difference in heat capacity between polymorphs ranges from +26% at 10 K to -3% at 300 K. The difference indicates the contribution into the heat capacity of piezoelectric gamma polymorph, probably connected with phase transition and ferroelectricity. Thermodynamic evaluations show that at ambient conditions gamma polymorph is stable and alpha polymorph is metastable.