K. S. Gavrichev

Fractal model of heat capacity for substances with diamond-like structures☆

Low temperature heat capacity models for substances with diamond-like structures have been considered on the basis of the Debye model and fractal states filling at fixed characteristic temperature. It was shown that low temperature calorimetry is an efficient tool for scanning the distribution of the atomic vibrational states in real substances. Fractal dimension and Poissons ratio in the elastic-isotropic multifractal model are related by a simple interdependence, which enables estimation of the fractal dimension from elastic properties of solids.

Revised heat capacity and thermodynamic functions of GdVO4

The heat capacity of GdVO4 has been determined by adiabatic calorimetry in the range 5–345 K. The present experimental data and earlier results have been used to evaluate the thermodynamic functions of gadolinium orthovanadate (Cp0(T), S0(T), H0(T) − H0(0), and Φ0(T)) as functions of temperature (5–350 K). Its Gibbs energy of formation is determined to be ΔfG0(GdVO4, 298.15 K) = −1684.5 ± 1.6 kJ/mol.

Heat capacity and thermodynamic functions of epsomite MgSO4 · 7 H2O at 0–303 K

Geological–geophysical data obtained by the Galileo spacecraft during its traveling around Jupiter’s satellites suggest the presence of a water layer (in terrestrial terms, marine or oceanic water) from tens (Europe) to a few hundred (Ganymede and Callisto) kilometers thick beneath an outer solid ice shell [1–2]. The oceans of Europa, Ganymede, and Callsito are supposedly high-pressure electrolytic solutions. The presence of water supports the hypotheses of the existence of primitive extraterrestrial life forms in the surface ocean. The outer shells of Jupiter’s icy satellites consist mainly of H 2 O ice contaminated with dark non-ice component (carbonaceous chondrite-type matter). The data obtained by the Galileo probe point out the presence of mixtures of salt crystal hydrates ( MgSO 4 · n H 2 O, Na 2 SO 4 · n H 2 O , and others) on the ice surface of the satellites [3].

Low-temperature heat capacity and thermodynamic properties of four boron nitride modifications

Abstract A short review of the low-temperature heat capacity studies of four boron nitride (BN) modifications is presented. C p versus ( T ) dependences of high-ordered hexagonal and disordered (turbostratic) modifications were studied by adiabatic calorimetry. The influence of disordering on the heat capacity of boron nitride is shown. The values of thermodynamic properties (heat capacity, entropy, enthalpy, and formation enthalpy) of four BN modifications is reported.

Heat capacity and thermodynamic functions of xenotime YPO4(c) at 0–1600 K

The heat capacity of xenotime YPO4(c) was measured by adiabatic calorimetry at 4.78–348.07 K. Our experimental and literature data on H0(T)-H0(298.15 K) of Y orthophosphate were utilized to derive the Cp0(T) function of xenotime at 0–1600 K, which was then used to calculate the values of thermodynamic functions: entropy, enthalpy change, and reduced Gibbs energy. These functions assume the following values at 298.15 K: Cp0 (298.15 K) = 99.27 ± 0.02 J K−1 mol−1, S0(298.15 K) = 93.86 ± 0.08 J K−1 mol−1, H0(298.15 K) − H0(0) = 15.944 ± 0.005 kJ mol−1, Φ0(298.15 K) = 40.38 ± 0.08 J K−1 mol−1. The value of the free energy of formation ΔfG0(YPO4, 298.15 K) is −1867.9 ± 1.7 kJ mol−1.

Heat Capacity and Thermodynamic Properties of Inorganic Compounds Containing Tetrahedral Anions (BH-4, AlH-4, GaH-4, BF-4, ClO-4, BrO-4, and IO-4)

Adiabatic and differential scanning calorimetry data are presented on the heat capacity of inorganic compounds containing tetrahedral anions. The entropy and enthalpy of phase transitions in these compounds are evaluated, and the mechanisms of the transitions are discussed in terms of orientational disordering. The heat capacity data are used to estimate, by an additive scheme, the frequencies of lattice (translational and librational) vibrations. It is shown that the BH-4 anion experiences hindered rotation in lattice sites, while the anions in the other complex hydrides, perhalates, and fluoroborates undergo librational vibrations.

The heat capacity and thermodynamic functions of EuPO4 over the temperature range 0-1600 K

The heat capacity of EuPO4 was measured by adiabatic calorimetry over the temperature range 9.81–298.48 K. The experimental and literature data were generalized to obtain the temperature dependence of the heat capacity of europium orthophosphate from 0 to 1600 K. This dependence was used to calculate thermodynamic functions (entropy, enthalpy, and reduced Gibbs energy). The data on the heat capacity of europium orthophosphate and diamagnetic lanthanum orthophosphate were used to estimate the noncooperative magnetic transition (Schottky anomaly) value.

Low-temperature heat capacity and thermodynamic functions of DyVO4

The heat capacity of dysprosium orthovanadate has been determined by adiabatic calorimetry in the range 6.12–343.26 K. The present and earlier data have been used to calculate the thermodynamic functions of DyVO4 in the temperature range 0–350 K. We have determined the absolute entropy and Gibbs energy of formation of dysprosium orthovanadate: S0(298.15 K) = 148.34 ± 0.11 J/(mol K), ΔfG0(298.15 K) = −1671.6 ± 2.1 kJ/mol. An anomaly has been detected at temperatures below 42 K, due to the Jahn-Teller phase transformation (TC = 14.42 K). We have determined the thermodynamic characteristics of the transformations in the temperature range 0–42.63 K.

Heat capacity and thermodynamic functions of YbPO4 from 0 to 1800 K

The thermodynamic functions of YbPO4 have been determined experimentally in the temperature range 6–1745 K. The results have been used to calculate temperature-dependent heat capacity, entropy, enthalpy increment, and reduced Gibbs energy of YbPO4 in the range 6–1800 K. The Gibbs energy of formation of ytterbium orthophosphate (ΔfG0(298.15 K)) has been determined.

Heat capacity and thermodynamic functions of LaVO4 and LuVO4 from 7 to 345 K

The heat capacities of lanthanum and lutetium orthovanadates have been measured at temperatures from 7 to 345 K using an adiabatic calorimeter. No anomalies have been detected in the heat capacity data. The thermodynamic functions (Cp0(T), S0(T), and H0(T) − H0(0)) of the two compounds have been calculated in the temperature range studied, and their Debye characteristic temperatures have been estimated.