Single crystals of undoped Li 2 WO 4 and Li 2 W 1-0.0125 Mo 0.0125 O 4 : formation enthalpies, heat capacity in the temperature range 320-997 K.

The Li ₂ WO ₄ single crystal was first grown by applying the Czochralski technique with weight control and low-temperature-gradients. A single crystal of Li ₂ WO ₄ is one of the perspective materials for researching rare events. The heat capacity for a Li ₂ W _1-0.0125 Mo _0.0125 O ₄ single crystal has been determined by DSC calorimetry in the temperature range 320-997 K for the first time. No anomalies in the heat capacity associated with phase transitions were found. The standard formation enthalpy for the Li ₂ WO ₄ single crystal was studied using reaction calorimetry. It has been shown that the relation of standard formation enthalpies for Li ₂ W _{1- x} Mo _x O ₄ ( x = 0.15-0) with function (1- x )W + x Mo are close to linear, which allows one to predict the thermodynamic properties for single crystals with isotopes Li ₂ W ¹⁸⁶ _1-0.0125 Mo ¹⁰⁰ _0.0125 O ₄ and Li ₂ W ¹⁸⁶ O ₄ . It was shown that single crystals with isotopes are more thermodynamically stable than without isotopes.