Statistical-thermodynamic description of the order–disorder transformation of D019-type phase in Ti–Al alloy

2008 ◽  
Vol 452 (1) ◽  
pp. 122-126 ◽  
Author(s):  
T.M. Radchenko ◽  
V.A. Tatarenko ◽  
H. Zapolsky ◽  
D. Blavette
Keyword(s):  
Thermodynamic Description ◽  
Statistical Thermodynamic ◽  
Al Alloy ◽  
Type Phase

Thermodynamics of Defect Formation and Hydration of Y2O3

2012 ◽  
Vol 326-328 ◽  
pp. 126-131 ◽  
Author(s):  
L.P. Putilov ◽  
V.I. Tsidilkovski ◽  
A.N. Varaksin ◽  
Anatoly Yakovlevich Fishman
Keyword(s):  
Electronic Structure ◽  
Gas Phase ◽  
Defect Formation ◽  
Thermodynamic Description ◽  
Statistical Thermodynamic ◽  
Wide Range ◽  
F Center ◽  
Mechanical Approach ◽  
Quantum Mechanical Approach ◽  
F Centers

Defect formation in yttria with a small content of acceptor impurities in equilibrium with a hydrogen-containing gas phase is studied theoretically. A statistical-thermodynamic description of the yttriagas equilibrium is based on the approach developed for compounds with a complex electronic structure [Phys. Stat. Sol. B (1991) Vol. 168, p. 233]. The considered model of electronic structure for Y2O3 includes, besides valence and conduction bands, acceptor and F-center states. The energy of F-centers was calculated in the framework of the variational quantum-mechanical approach combined with the molecular statics method. It is shown that acceptor states appreciably affect the thermodynamics of defect formation, while the F-centers contribution in a wide range of external parameters is small. The concentrations of defects (protons, oxygen vacancies, electronic defects) and the Fermi level position are determined as functions of temperature and gas phase parameters.

scholarly journals Thermodynamic Formulations of Excess and Absolute Values of Adsorption on Solid Surfaces: A Comparison of One- and Two-Phase Approaches

1986 ◽  
Vol 3 (4) ◽  
pp. 271-291 ◽  
Author(s):  
H. Wittkopf ◽  
P. Bräuer
Keyword(s):  
High Pressures ◽  
Thermodynamic Description ◽  
Solid Surfaces ◽  
Statistical Thermodynamic ◽  
Two Phase ◽  
Phase Approach ◽  
Adsorption Analysis ◽  
Basic Concepts ◽  
The Difference ◽  
The One

The generally used methods of thermodynamic adsorption analysis are summarized in two basic concepts: the two-phase approach (which is an adequate picture of volume phase thermodynamics in adsorption) and the one-phase approach (which uses excess values for the thermodynamic description of adsorption). Differential and integral molar values of adsorption Δ a X̄ and Δ a X in the two-phase approach are not identical with the corresponding excess values Δ a X̄s and Δ a Xs in the one-phase approach. Especially at high temperatures and high pressures they may be entirely different. It is shown that the experimental methods most usually in adsorption thermodynamics (as adsorption volumetry and gravimetry) give excess data which are to be used in the one-phase approach but which can be transformed to the two-phase approach. Using statistical thermodynamic calculations the difference between these basic concepts is shown over a wide temperature range for the first virial coefficient, the internal energy and the heat capacity of adsorption.

Statistical thermodynamic description of H2 molecules in normal ortho/para mixture

2012 ◽  
Vol 37 (12) ◽  
pp. 9656-9668 ◽  
Author(s):  
Gianpiero Colonna ◽  
Antonio D'Angola ◽  
Mario Capitelli
Keyword(s):  
Thermodynamic Description ◽  
Statistical Thermodynamic

scholarly journals Martensitic αʺ-Fe16N2-Type Phase of Non-Stoichiometric Composition: Current Status of Research and Microscopic Statistical-Thermodynamic Model

2020 ◽  
Vol 21 (4) ◽  
pp. 580-618
Author(s):  
Taras Radchenko ◽  
◽  
Oleksandr Gatsenko ◽  
Vyacheslav Lizunov ◽  
Valentyn Tatarenko ◽  
...  
Keyword(s):  
Thermodynamic Model ◽  
Permanent Magnets ◽  
Stoichiometric Composition ◽  
Equilibrium Concentration ◽  
Theoretical Data ◽  
Crystalline Lattice ◽  
Current Status ◽  
Statistical Thermodynamic ◽  
Type Phase ◽  
Wide Range

The literature (experimental and theoretical) data on the tetragonality of martensite with interstitial–substitutional alloying elements and vacancies are reviewed and analysed. Special attention is paid to the studying the martensitic αʺ-Fe16N2-type phase with unique and promising magnetic properties as an alternative to the rare-earth intermetallics or permendur on the world market of the production of permanent magnets. The period since its discovery to the current status of research is covered. A statistical-thermodynamic model of ‘hybrid’ interstitial–substitutional solid solution based on a b.c.t. crystal lattice, where the alloying non-metal constituents (impurity atoms) can occupy both interstices and vacant sites of the host b.c.c.(t.)-lattice, is elaborated. The discrete (atomic-crystalline) lattice structure, the anisotropy of elasticity, and the ‘blocking’ and strain-induced (including ‘size’) effects in the interatomic interactions are taken into account. The model is adapted for the non-stoichiometric phase of Fe–N martensite maximally ordered by analogy with αʺ-Fe16N2, where nitrogen atoms are in the interstices and at the sites of b.c.t. iron above the Curie point. It is stressed an importance of adequate data on the available (in the literature) temperature- and concentration-dependent microscopic energy parameters of the interactions of atoms and vacancies. The features of varying (viz. non-monotonic decreasing with increasing temperature) the relative concentration of N atoms in the octahedral interstices of b.c.t. Fe, and therefore, the degree of its tetragonality (correlating with this concentration) are elucidated. Within the wide range of varying the total content of introduced N atoms, the ratio of the equilibrium concentration of residual site vacancies to the concentration of thermally activated vacancies in a pure b.c.c. Fe is demonstrated at a fixed temperature.

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