The isochoric heat capacity of ZrW2O8 and Sc2W3O12 is greater than their isobaric one

• Isochoric heat capacity for negative thermal expansion is larger than isobaric one.
• Isentropic compressibility for negative expansion is larger than isothermal one.
• Big deviations from the Mayer's relation are found.

It is shown from experimental data that the isochoric heat capacity of the negative thermal expansion substances ZrW2O8 and Sc2W3O12 is larger than their isobaric one. This is in agreement with the theory developed earlier by the author. Their isentropic compressibility is also larger than their isothermal compressibility. It is possible that this result is valid also for Y2Mo3O12.