[en] Second law of thermodynamics states that entropy production rate is always positive in a system under an external forcing. However, this statement is based on an average behavior of such a system. In principle, one can observe negative entropy production rate in small systems observed for a finite time. Fluctuation theorem (FT) proposed by Evans, Cohen and Morris is based on the probability of occurrence of such rare negative entropy events in a non-equilibrium system under steady state. FT theorem has been verified in many near-equilibrium systems, however, until the advent of this work no such conclusive test in far-from-equilibrium systems has been made. In this work, using 2D molecular dynamics simulations, we propose to test the fluctuation theorem in Rayleigh-Benard convection of Yukawa liquids taken as an example of far-from-equilibrium system. Under the action of external gravity and external temperature gradient, system is evolved to attain a steady state beyond a critical value of temperature gradient. In this steady state, we study the instantaneous local entropy production rate and compare the results with the predictions of fluctuation theorem, the details of which will be presented. (author)

[en] The standard free energy of formation for zirconium molybdate (ZrMo₂O₈) was derived from its vapour pressure measured in the temperature range 1029 to 1142 K employing the transpiration technique. ZrMo₂O₈ vaporizes incongruently according to the reaction n< ZrMo₂O₈>→n< ZrO₂>+2(MoO₃)_n, n=3, 4, 5. The standard free energy of formation of ZrMo₂O₈ calculated from the partial pressure of (MoO₃)₃ in the vapour above ZrMo₂O₈+ZrO₂ mixture could be expressed by the relation Δ_fG < ZrMo₂O₈>=(-2525.5±4.9)+(0.6115±0.0045)T kJ/mol (1029)< T/K<1142). The values of Δ_fG < ZrMo₂O₈> obtained in this work agree very well with those reported recently from solid electrolyte galvanic cell measurements. (orig.)

[en] Short communication

[en] Enthalpies of formation of the intermetallic compounds, UGa₂ and UGa₃, at 298.15 K were determined by using high-temperature liquid gallium solution calorimetric measurements at 1427 K to be -40.4±6.0 and -38.3±4.4 kJ gatom^-1, respectively. The enthalpies of formation of UGa₂ at 1563 K and UGa₃ at 1038 K were determined to be -79.1±2.5 and -40.6±1.5 kJ gatom^-1 by using the precipitation calorimetric method. The enthalpies of formation of UGa₃ at 298.15 and at 1038 K are found to be in agreement with each other, whereas that of UGa₂ at 1563 K is highly exothermic compared to that at 298.15 K. (orig.)

[en] Standard molal Gibbs energy of formation and entropy data for simple neptunium solids and aqueous neptunium complexes with OH^-, Cl^-, F^-, CO₃^2-, PO₄^3-, SO-4^2- and Na⁺ have been critically reviewed. Selected values are used with estimated heat capacity values to derive self-consistent analytical expressions for the temperature dependence of the standard molal Gibbs energies of formation of the species from 25 to 150 degrees C. The Gibbs energies have been used to evaluate the effect of different concentrations of ligands on the solubility of neptunium solids as a function of temperature. Potential-pH diagrams are given for neptunium in pure water and in two model groundwaters. Important deficiencies in the available thermodynamic data for neptunium species are discussed

[en] We develop further our analysis of the third law of thermodynamics; in particular, we discuss further conditions ensuring the validity of the third law of thermodynamics in its entropic form (N). The introduction in standard homogeneous thermodynamics of the framework in which the absolute temperature T appears as an independent coordinate for the entropy S is followed by the introduction of a more general framework in which Gibbs thermodynamic space, where only extensive independent coordinates appear, is suitably generalized. General properties of S are also discussed. An analysis of the differential conditions which can ensure the validity of (N) follows. Then, we introduce a condition involving the behaviour of generalized heat capacities along curves leaving the surface T = 0 and we show that, under suitable mathematical conditions, it is equivalent to (N). The physical meaning of this condition is also clarified, and amounts to the impossibility for a system to leave a state at T = 0 without heat absorption. Then, we show that a condition of minimum entropy at T = 0 is again equivalent to (N) under suitable conditions. Some notes about (N) when one allows deformation coordinates to be divergent as T → 0⁺ and about phase coexistence and mixtures also appear

[en] The enthalpies of formation of seven hydrogen vanadium bronzes, H_xV₂O₅(0 < x ≤ 3.77), prepared at ambient temperature by 'hydrogen spillover', have been determined by solution calorimetry. The stabilities of the compounds towards decomposition, disproportionation and oxidation are discussed. 19 refs.; 2 figs.; 6 tabs

[en] The free enthalpy of formation of Fe₂W, Fe₃W₂ and FeWO₄ was determined by emf-measurements. (orig.)

No abstract available

[en] The emf of the galvanic cells Pt, Mo, MoO₂vertical stroke8 YSZvertical stroke''FeO'', Fe, Pt (I) and Pt, Fe, ''FeO''vertical stroke8 YSZvertical strokeMoO₂, Mo₃Te₄, MoTe₂(α), C, Pt (II) were measured over the temperature ranges 837 to 1151 K and 775 to 1196 K, respectively, using 8 mass% yttria-stabilized zirconia (8 YSZ) as the solid electrolyte. From the emf values, the partial molar Gibbs energy of solution of molybdenum in Mo₃Te₄/MoTe₂(α), Δanti G_Mo was found to be Δanti G_Mo±1.19 (kJ/mol)=-025.08+0.00420T(K). Using the literature data for the Gibbs energy of formation of MoTe₂(α), the expression ΔG_f⁰(Mo₃Te₄, s)±5.97 (kJ/mol)=-253.58+0.09214T(K) was derived for the range 775 to 1196 K. A third-law analysis yielded a value of -209±10 kJ/mol for ΔH⁰_f,298 of Mo₃Te₄(s). (orig.)