Thermodynamic, thermochemical and thermophysical properties of HgBr2

For mercury dibromide HgBr2, a promising component of the work-ing mixture of gas-discharge exciplex sources of coherent (lasers) and spontaneous (exciplex lamps) radiation, as well as a promising nonlin-ear optical crystal for the infrared radiation process, thermodynamic and thermochemical properties in the temperature range 173-512 K were investigated. The established basic thermodynamic (isobaric heat capacity Cp, total entropy S, enthalpy H and Gibbs energy G) and ther-mochemical (enthalpy AHf and Gibbs energy AGf of formation) func-tions of HgBr2 were compared with the known literature data at 298- 514 K. The obtained results differed from the literature within 1-2% (for Cp), 0.1-0.2% (for S, H and G) and 0.1-0.6% (for AHf and AGf). The experimental data, combined with semi-empirical approaches and ab initio calculations taken from the literature, were used to estimate the previously unknown additional thermodynamic and thermophysi-cal properties of HgBr2: isochoric heat capacity CV, Debye tempera-ture & theta;D, volume thermal expansion & alpha;V, isothermal compressibility & beta;T (isothermal bulk modulus BT = 1/& beta;T), Gruneisen constant & gamma;G, phonon longitudinal vl, transverse vs, average v- velocities and phonon thermal conductivity & kappa;. In the present work, it was found that crystalline mer-cury dibromide expands strongly upon heating and has a low phonon thermal conductivity.