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I Manna - One of the best experts on this subject based on the ideXlab platform.
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prediction of enthalpy of formation and Gibbs Energy change in pseudo binary ti zr fe cr 2 and pseudo ternary ti zr fe cr 2 h system using extended miedema model
Journal of Materials Science, 2007Co-Authors: S Bera, Sagnik Mazumdar, M Ramgopal, Souvik Bhattacharyya, I MannaAbstract:The thermodynamic model proposed by Miedema is capable of predicting the enthalpy of formation (ΔH) and relative stability of phases in binary but not in ternary or multi-component systems. While developing nanocrystalline binary/ternary metal hydrides for compressor-driven reversible heating–cooling applications, it is necessary to identify appropriate alloy compositions with suitable hydrogen storage capacity and reversible hydrogen absorption–desorption capability. Accordingly, a suitable modification of the Miedema model is proposed in the present study for calculating ΔH of AB2 type of pseudo-binary (Ti–Zr)(Fe–Cr)2 and pseudo-ternary (Ti–Zr)(Fe–Cr)2-H alloys. Subsequently, Gibbs Energy (ΔG) of the possible phases is estimated to predict relative phase stability/equilibrium in a given system. It is shown that grain size or interfacial Energy contribution exerts a significant influence on ΔG and relative stability of the phases beyond a critical value/limit. Finally, the predicted phase equilibrium from this model-based calculation is validated by suitable comparison with relevant experimental data reported in the literature.
S Bera - One of the best experts on this subject based on the ideXlab platform.
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prediction of enthalpy of formation and Gibbs Energy change in pseudo binary ti zr fe cr 2 and pseudo ternary ti zr fe cr 2 h system using extended miedema model
Journal of Materials Science, 2007Co-Authors: S Bera, Sagnik Mazumdar, M Ramgopal, Souvik Bhattacharyya, I MannaAbstract:The thermodynamic model proposed by Miedema is capable of predicting the enthalpy of formation (ΔH) and relative stability of phases in binary but not in ternary or multi-component systems. While developing nanocrystalline binary/ternary metal hydrides for compressor-driven reversible heating–cooling applications, it is necessary to identify appropriate alloy compositions with suitable hydrogen storage capacity and reversible hydrogen absorption–desorption capability. Accordingly, a suitable modification of the Miedema model is proposed in the present study for calculating ΔH of AB2 type of pseudo-binary (Ti–Zr)(Fe–Cr)2 and pseudo-ternary (Ti–Zr)(Fe–Cr)2-H alloys. Subsequently, Gibbs Energy (ΔG) of the possible phases is estimated to predict relative phase stability/equilibrium in a given system. It is shown that grain size or interfacial Energy contribution exerts a significant influence on ΔG and relative stability of the phases beyond a critical value/limit. Finally, the predicted phase equilibrium from this model-based calculation is validated by suitable comparison with relevant experimental data reported in the literature.
Kazuhiro Nagata - One of the best experts on this subject based on the ideXlab platform.
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Gibbs Energy Change of Carbothermal Nitridation Reaction of Al2O3 to Form AlN and Reassessment of Thermochemical Properties of AlN
Journal of the American Ceramic Society, 2004Co-Authors: Wataru Nakao, Hiroyuki Fukuyama, Kazuhiro NagataAbstract:The experimental method for the high-temperature reaction equilibria in the AlN-Al2O3 system has been established. The equilibrium N2-CO gas compositions coexisting with AlN- Al2O3-graphite have been successfully measured by quadrupole mass spectrometry and gas chromatography. From the obtained results, the standard Gibbs Energy change of the forming reaction of AlN by carbothermal nitridation is determined at temperatures ranging from 1723 to 1899 K: From the obtained result, the standard Gibbs Energy of formation of AlN and the third-law enthalpy of formation of AlN at 298.15 K are derived as The disagreement between the present results and values in the NIST–JANAF thermodynamic table is discussed.
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determination of Gibbs Energy of formation of cuspidine 3cao 2sio2 caf2 by transpiration method
Isij International, 2004Co-Authors: Hiroyuki Fukuyama, Hideki Tabata, Tadayuki Oshima, Kazuhiro NagataAbstract:The standard Gibbs Energy change of the following reaction of cuspidine (3CaO.2SiO 2 .CaF 2 ) with water vapor has been determined by a transpiration method as 3CaO.2SiO 2 .CaF 2 (s)+H 2 O(g)=2(2CaO.SiO 2 )(s)+2HF(g) Δ r G°/kJ=265-0.116T (′16) (1 221
Gibbs Energy of formation of cuspidine has been evaluated as, Δ f G°(cuspidine)/kJ mol - 1 = -5 178+0.813T(′19) (1 221 thermodynamic data. -
determination of Gibbs Energy of formation of cuspidine 3cao 2sio2 caf2 from the electromotive force method using caf2 as the solid electrolyte
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2003Co-Authors: Hiroyuki Fukuyama, Hideki Tabata, Kazuhiro NagataAbstract:The standard Gibbs Energy change for the following reaction has been directly determined by electromotive force (EMF) measurement using CaF2 as the solid electrolyte in the temperature range from 1313 to 1329 K. $$\begin{gathered} 3CaO \cdot 2SiO_2 \cdot CaF_2 (s) + CaO(s) = 2(2CaO \cdot SiO_2 )(s) + CaF_2 (s) \hfill \\ \Delta _r G^ \circ /kJ = 15.9 - 0.0192T( \pm 0.2) \hfill \\ \end{gathered} $$ From the preceding results, the standard Gibbs Energy of formation of cuspidine has been evaluated for the first time as $$\Delta _f G^ \circ (cuspidine)/kJmol^{ - 1} = - 5198 + 0.825T( \pm 12)$$ The chemical potential diagram for the CaO-SiO2-CaF2 system has been developed at 1323 K based on the thermodynamic data obtained in the present study.
Christoph Held - One of the best experts on this subject based on the ideXlab platform.
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standard Gibbs Energy of metabolic reactions v enolase reaction
Biochimica et Biophysica Acta, 2020Co-Authors: Thorsten Greinert, Kristina Vogel, Astrid Ina Seifert, Riko Siewert, Irina V Andreeva, Sergey P Verevkin, Thomas Maskow, Gabriele Sadowski, Christoph HeldAbstract:Abstract The glycolytic pathway is one of the most important pathways for living organisms, due to its role in Energy production and as supplier of precursors for biosynthesis in living cells. This work focuses on determination of the standard Gibbs Energy of reaction ΔRg′0 of the enolase reaction, the ninth reaction in the glycolysis pathway. Exact ΔRg′0 values are required to predict the thermodynamic feasibility of single metabolic reactions or even of metabolic reaction sequences under cytosolic conditions. So-called “apparent” standard data from literature are only valid at specific conditions. Nevertheless, such data are often used in pathway analyses, which might lead to misinterpretation of the results. In this work, equilibrium measurements were combined with activity coefficients in order to obtain new standard values ΔRg′0 for the enolase reaction that are independent of the cytosolic conditions. Reaction equilibria were measured at different initial substrate concentrations and temperatures of 298.15 K, 305.15 K and 310.15 K at pH 7. The activity coefficients were predicted using the equation of state electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT). The ePC-SAFT parameters were taken from literature or fitted to new experimentally determined osmotic coefficients and densities. At 298.15 K and pH 7, a ΔRg′0(298.15 K, pH 7) value of −2.8 ± 0.2 kJ mol−1 was obtained. This value differs by up to 5 kJ mol−1 from literature data. Reasons are the poorly defined “standard” conditions and partly undefined reaction conditions of literature works. Finally, using temperature-dependent equilibrium constants and the van ‘t Hoff equation, the standard enthalpy of reaction of ΔRh′0(298.15 K, pH 7) = 27 ± 10 kJ mol−1 was determined, and a similar value was found by quantum-chemistry calculations.
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standard Gibbs Energy of metabolic reactions iii the 3 phosphoglycerate kinase reaction
ACS omega, 2018Co-Authors: Anton Wangler, Gabriele Sadowski, Christina Schmidt, Christoph HeldAbstract:The glycolytic pathway is one of the most studied metabolic pathways to date. This work focuses on determining the standard Gibbs Energy of reaction (ΔRg0) of the first adenosine triphosphate-yielding reaction step of glycolysis, namely, the 3-phosphoglycerate kinase (PGK) reaction. Trustworthy values of ΔRg0 are required for thermodynamic approaches to determine single reaction conversions or even fluxes of metabolic reactions. In literature, the observed ΔRg0,obs values are usually determined directly from the experimental equilibrium composition data without accounting for the nonideality of the reaction mixture. That is the reason why the observed ΔRg0,obs values do not present consistent standard data as they are a function of the concentration, pH, and pMg. In this work, a combination of experimentally determined equilibrium composition data and activity coefficients of the reacting agents was used to determine ΔRg0 values for the temperatures 303, 313, and 323 K at pH 7. The activity coefficients w...
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standard Gibbs Energy of metabolic reactions ii glucose 6 phosphatase reaction and atp hydrolysis
Biophysical Chemistry, 2017Co-Authors: Florian Meurer, Gabriele Sadowski, Hoang Tam Do, Christoph HeldAbstract:Abstract ATP (adenosine triphosphate) is a key reaction for metabolism. Tools from systems biology require standard reaction data in order to predict metabolic pathways accurately. However, literature values for standard Gibbs Energy of ATP hydrolysis are highly uncertain and differ strongly from each other. Further, such data usually neglect the activity coefficients of reacting agents, and published data like this is apparent (condition-dependent) data instead of activity-based standard data. In this work a consistent value for the standard Gibbs Energy of ATP hydrolysis was determined. The activity coefficients of reacting agents were modeled with electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT). The Gibbs Energy of ATP hydrolysis was calculated by combining the standard Gibbs energies of hexokinase reaction and of glucose-6-phosphate hydrolysis. While the standard Gibbs Energy of hexokinase reaction was taken from previous work, standard Gibbs Energy of glucose-6-phosphate hydrolysis reaction was determined in this work. For this purpose, reaction equilibrium molalities of reacting agents were measured at pH 7 and pH 8 at 298.15 K at varying initial reacting agent molalities. The corresponding activity coefficients at experimental equilibrium molalities were predicted with ePC-SAFT yielding the Gibbs Energy of glucose-6-phosphate hydrolysis of − 13.72 ± 0.75 kJ·mol− 1. Combined with the value for hexokinase, the standard Gibbs Energy of ATP hydrolysis was finally found to be − 31.55 ± 1.27 kJ·mol− 1. For both, ATP hydrolysis and glucose-6-phosphate hydrolysis, a good agreement with own and literature values were obtained when influences of pH, temperature, and activity coefficients were explicitly taken into account in order to calculate standard Gibbs Energy at pH 7, 298.15 K and standard state.
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standard Gibbs Energy of metabolic reactions i hexokinase reaction
Biochemistry, 2016Co-Authors: Florian Meurer, Gabriele Sadowski, Maria Bobrownik, Christoph HeldAbstract:The standard Gibbs Energy of reaction enables calculation of the driving force of a (bio)chemical reaction. Gibbs energies of reaction are required in thermodynamic approaches to determine fluxes as well as single reaction conversions of metabolic bioreactions. The hexokinase reaction (phosphorylation of glucose) is the entrance step of glycolysis, and thus its standard Gibbs Energy of reaction (ΔRg°) is of great impact. ΔRg° is accessible from equilibrium measurements, and the very small concentrations of the reacting agents cause usually high error bars in data reduction steps. Even worse, works from literature do not account for the nonideal behavior of the reacting agents (activity coefficients were assumed to be unity); thus published ΔRg° values are not standard data. Consistent treatment of activity coefficients of reacting agents is crucial for the accurate determination of standard Gibbs Energy from equilibrium measurements. In this work, equilibrium molalities of hexokinase reaction were measure...
Aaron M. Holder - One of the best experts on this subject based on the ideXlab platform.
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Physical descriptor for the Gibbs Energy of inorganic crystalline solids and temperature-dependent materials chemistry
Nature Communications, 2018Co-Authors: Christopher J. Bartel, Samantha L. Millican, Ann M. Deml, John R. Rumptz, William Tumas, Alan W. Weimer, Stephan Lany, Vladan Stevanović, Charles B. Musgrave, Aaron M. HolderAbstract:Materials databases currently neglect the temperature effect on compound thermodynamics. Here the authors introduce a Gibbs Energy descriptor enabling the high-throughput prediction of temperature-dependent thermodynamics across a wide range of compositions and temperatures for inorganic solids. The Gibbs Energy, G , determines the equilibrium conditions of chemical reactions and materials stability. Despite this fundamental and ubiquitous role, G has been tabulated for only a small fraction of known inorganic compounds, impeding a comprehensive perspective on the effects of temperature and composition on materials stability and synthesizability. Here, we use the SISSO (sure independence screening and sparsifying operator) approach to identify a simple and accurate descriptor to predict G for stoichiometric inorganic compounds with ~50 meV atom^−1 (~1 kcal mol^−1) resolution, and with minimal computational cost, for temperatures ranging from 300–1800 K. We then apply this descriptor to ~30,000 known materials curated from the Inorganic Crystal Structure Database (ICSD). Using the resulting predicted thermochemical data, we generate thousands of temperature-dependent phase diagrams to provide insights into the effects of temperature and composition on materials synthesizability and stability and to establish the temperature-dependent scale of metastability for inorganic compounds.