Thermodynamic properties and phonon density of states of Na2Mo2O7 using heat capacity measurements from 5.7 to 310 K

The study results of disodium dimolybdate single crystal are presented on the basis of experimentally obtained data on heat capacity. The heat capacity of Na2Mo2O7 was measured by the adiabatic method in the range of 5.7–310 K. No anomalies in the heat capacity associated with the phase transition were found. Extrapolation of the heat capacity to 0 K by a physically reasonable equation was performed. The Debye temperature at absolute zero was obtained. Based on the experimental heat capacity, the phonon density of states and isobaric thermodynamic functions (entropy, enthalpy increment, and Gibbs free energy) from 0 to 310 K were calculated. Using information on Na2Mo2O7 density of states, zero-point energy and isochoric thermodynamic functions (entropy, internal energy increment, and reduced Helmholtz energy) from 0 to 848 K were calculated. The approach used to obtain the characteristics of solids is general and can be used to study a wide range of objects. •Low temperature heat capacity of Na2Mo2O7 single crystal was measured.•Isobaric entropy, enthalpy, and Gibbs free energy were calculated.•Debye characteristic temperature at absolute zero was calculated.•Phonon density of states and zero-point energy were obtained.•Isochoric entropy, internal energy, and reduced Helmholtz energy were calculated.