Thermodynamics of oxygen in CaMnO3 − δ

The experimental data for equilibrium oxygen content were used in order to extract increments of partial molar thermodynamic functions of oxygen with changes of oxygen stoichiometry in calcium manganite CaMnO_3???δ . It is shown that along with the oxygen exchange reaction, thermal excitation of Mn⁴⁺ cations plays an important role in equilibration of charged manganese species that appear in response to the loss of oxygen at heating. The interrelation of partial molar enthalpy and entropy of oxygen with electron and ion defect formation parameters is obtained in approximation of the point defect model. The nearly linear changes of oxygen partial molar enthalpy are shown to directly reflect thermally driven changes in concentration of Mn³⁺ cations.     

Reaction reversibility in α-pinene thermal isomerization: improving the kinetic model

Revision of the experimental data on α-pinene thermal isomerization attained in supercritical ethanol allowed us to expand the reaction scheme, which includes now six main products and eleven reversible reactions. The equilibrium constants of every reaction (K _{T, j} and K _Φ, j) were calculated to allow for reversibility of reactions. The thermochemical data of the pure compounds required to calculate constants K _{T, j} and K _{Φ, j} (standard enthalpy and entropy of formation Δ_f H° (298.15 K), Δ_f S° (298.15 K), heat capacity C _p (T), critical parameters T _cr and p _cr, boiling point T _b, and the acentric factor ω) were preliminary estimated using the empirical Joback and Benson methods. A kinetic model based on the new expanded scheme of reversible reactions was successfully identified and its kinetic parameters k _j (600 K) and E _j were determined. Detailed examination of the new kinetic model allowed us to refine the generally accepted mechanism of α-pinene thermal isomerization and to distinguish additional features of the multistep process.     

Laser Gain for Inhomogeneous Boundary Conditions

Russian Physics Journal - The method proposed by the authors for solving the Helmholtz equation with homogeneous boundary conditions was verified for an elliptic cross section. The method is...     

ChemInform Abstract: First‐Principles Calculations of the Elastic and Electronic Properties of the Cubic Perovskites SrMO3 (M: Ti,V, Zr and Nb) in Comparison with SrSnO3.

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