New Features of Entall Database: Comparison of Experimental and Model Formation Enthalpies/ Nowe Funkcje Bazy Danych Entall: Porównanie Doświadczalnych I Modelowych Entalpii Tworzenia

Abstract

This paper presents a new version of the Entall database of the thermodynamic properties of metals and their alloys. The changes are related to the thermodynamic data of new binary and ternary systems as well as the integration of the database with an application for the modeling of the formation enthalpies of intermetallic phases with the use of the Miedema model. Using this tool, calculations of the enthalpies of formation of 38 intermetallic phases from 12 binary systems were performed and a comparative analysis conducted. The results of the analysis clearly showed a weak correlation between the model and experimental data. To improve this correlation, an intermediate method of proportional change was proposed, on the basis of the measurement of the enthalpy of formation for one of the phases. The values for the other phases obtained from this indirect method should not deviate much from the experimental ones provided that before the measurements (dissolving or pulping) or after them (direct synthesis), the phase being examined should undergo structural tests, in order to confirm its dominating amount in the samples.Keywords: COST 535, database, thermodynamic properties, Miedema model W pracy przedstawiona została nowa wersja bazy właściwości termodynamicznych metali i stopów Entall. Modyfikacja dotyczyła z jednej strony danych termodynamicznych nowych układów dwu i trójskładnikowych a z drugiej zaadaptowania do niej opracowanego programu (kalkulatora) do modelowania entalpii tworzenia faz międzymetalicznych modelem Miedemy. Korzystając z tego nowego narzędzia wykonane zostały obliczenia entalpii tworzenia dla 38 faz międzymetalicznych z 12 układów dwuskładnikowych oraz przeprowadzona została analiza porównawcza. Wyniki analizy pokazały jednoznacznie słabą korelację między danymi modelowymi i doświadczalnymi. Dla poprawienia tej korelacji zaproponowana została pośrednia metoda proporcjonalnej zmiany w oparciu o pomiar entalpii tworzenia dla jednej z faz. Uzyskane z tej pośredniej metody wartości dla innych faz powinny niewiele odbiegać od eksperymentalnych przy spełnieniu warunku, że faza dla której wykonywane były badania została przed pomiarami (rozpuszczanie lub roztwarzanie) lub po nich (bezpośrednia synteza) poddana badaniom strukturalnym, w celu potwierdzenia jej dominującej ilości w próbkach.

Calorimetric Measurements of Ga-Li System by Direct Reaction Method

“…The correlation analysis of the formation enthalpy data for the Ga-Li intermetallic phases showed that those calculated by the Miedema model [15,17] are much more exothermic than calculated data (presented by Yuan et al [12] and DFT calculations) as well as the ones from this study. Taking into consideration the experimental problems indicated in this studies and the fact that the results of Yuan et al [12] are one of the possible propositions of optimization, the last three sets of data could be thought of as comparable at this stage of investigations.…”

“…The obtained experimental data of the formation enthalpy of the alloys whose concentrations correspond to the Ga-Li intermetallic phases are shown in Table 2, together with the data calculated by Yuan et al [12], the data calculated by the Miedema model, which were obtained with the use of the Entall Miedema calculator [17] and DFT calculations [18]. Because, the obtained results of formation enthalpy for temperature range of 463-891 K do not vary significantly with the enthalpy of formation data calculated for 298 K, it may indicate lack of the temperature dependence of formation enthalpy of Ga-Li intermetallic phases.…”

Evaluation of microstructural and corrosion resistance of as-cast Cu45Mn25Al15Fe5Cr5Ni5 high entropy alloy

“…Table 3 shows the binary enthalpy of mixing values based on Miedema semi-empirical model. In addition, the enthalpy of formation for Cu-Cr with atomic ration 1:1 is 18.530117 kJ mol −1 , ΔH (Cu in Cr) is 49.286705 kJ mol −1 , and ΔH (Cr in Cu) is 49.793041 kJ mol −1 [29]. As a result of positive enthalpy of mixing, segregation phenomenon will be promoted leading to the formation of ID rich in Cr and Fe.…”

Elastic versus Alloying Effects in Mg-Based Hydride Films

“…By applying the same reasoning to the case of Pd-capped thin films of pure magnesium [9], in which Mg and Pd form an alloy only at a very thin (less than 2 nm thick) Mg=Pd interface, it is clear that the alloying model of Chung et al [10] cannot explain the observed large increases of hydrogen loading pressure for films as thick as 40 nm. Furthermore, as Mg and Ni have an enthalpy of mixing (H mix MgNi ¼ −5.6 kJ=mol) that is an order of magnitude smaller than the one of Mg with Pd (H mix MgPd ¼ −43 kJ=mol) [30,31], the model of Chung et al would predict large differences for the loading pressures of Ni-and Pd-capped Mg films. This prediction is contrary to what we observed experimentally [9].…”