Relationship between compressibility and hydrogen absorption in some Haucke compounds

Crivello, Jean-Claude; Gupta, Michèle

doi:10.1016/j.jallcom.2004.09.079

Cited by 9 publications

(4 citation statements)

References 24 publications

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“…About the A 2 Ni 7 H 8 hydrides, DFT shows that the formation becomes more exothermic in the order A = Y (−25.6 kJ/mol-H 2 ) → Gd (−27.1 kJ/mol-H 2 ) → Sm (−30.3 kJ/mol-H 2 ). This is in agreement with the correlation between the calculated rigidity of the intermetallic compounds, shown in Figure 6, and the values of Δ f H, as shown in the previous work on Haucke phase: 43 the most compressible intermetallics lead to the most stable hydrides. However, the experimental measurements present a different order of hydride stability, A = Sm (−19.7 kJ/mol-H 2 ) → Gd (−20.0 kJ/mol-H 2 ) 12 → Y (−23.0 kJ/mol-H 2 ).…”

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confidence: 92%

Experimental and Theoretical Investigations on the Influence ofAon the Hydrogen Sorption Properties ofANi_yCompounds,A= {Y, Sm, Gd}

et al. 2019

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The phase stability, electronic structure, magnetic and mechanical properties of ANi y compounds, A = {Y, Sm, Gd}, y = {2, 3, , , 4, 5}, and A 2Ni7H8 hydrides have been investigated by systematic first-principles calculations. Supported by a discussion to understand the role of A and y parameters, the results are compared with published and new experimental data regarding the heat of formation of some compounds and their hydrides. The main results can be summarized as follows: (i) ANi3 and A 2Ni7 are clearly stable by the density functional theory calculation, whereas the stability of ANi y for is not highlighted distinctively, in agreement with the difficulty to identify a single phase by experimental synthesis for some compounds such as Y5Ni19; (ii) ANi y compounds are found more rigid for A = Y and may explained the difficulty to observe Y5Ni19 in comparison with Sm5Ni19 and Gd5Ni19; and (iii) the calculated and measured heats of formation of A 2Ni7H8 hydrides are found in good agreement, around −25 to −30 kJ/mol-H2 according to the system.

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confidence: 92%

Experimental and Theoretical Investigations on the Influence ofAon the Hydrogen Sorption Properties ofANi_yCompounds,A= {Y, Sm, Gd}

et al. 2019

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“…These results may also be correlated to the H absorption properties of these phases. It is known in the AB 5 Haucke phase that the most compressible materials correspond to the most stable hydride, i.e., the lowest plateau pressure P H 2 in isothermal conditions. Thus, the increase of B for LaNi y compounds when n increases may partially explain the increase of their P H 2 .…”

Section: Resultsmentioning

confidence: 99%

Structural Stability of AB_y Phases in the (La,Mg)–Ni System Obtained by Density Functional Theory Calculations

2011

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Conflicting results on the La–Ni phase diagram still exist about the equilibrium state of intermetallic compounds such as La2Ni7 and La5Ni19. Moreover, the substitution of the rare earth by Mg element increases doubts about the phase stability in the La–Mg–Ni ternary system. In this paper, the stability of the AB y phase, where y = (5n + 4)/(n + 2) and n = 1–5, has been studied in the ternary system, with A = La, Mg and B = Ni. The AB y phase formation is explained by the stacking along the c axis of n × [AB 5] + [A 2 B 4] units following two possible sequences, one of rhombohedral and the other of hexagonal symmetry, called, respectively, 3R and 2H. Using Density Functional Theory (DFT) calculations, origins of the observed polymorphic features will be highlighted. A systematic study of every ordered configuration of (La,Mg)Ni3, (La,Mg)2Ni7, (La,Mg)5Ni19, some (La,Mg)6Ni24, and the hypothetical La7Ni29 is presented. From the estimation of the heats of formation, the preferential A site occupation by La and Mg is discussed among the various A crystallographic available sites. Depending on the AB y compound, results allow us to predict which of the 3R or 2H symmetry is the most stable at 0 K as a function of the La–Mg–Ni elemental composition. Crystallographic properties are compared to available experimental results.

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“…However, the elastic properties of LaNi 5−x Al x have been calculated relatively little in theory so far, only the elastic constants of LaNi 5 alloy were calculated by pseudo-potential method with plane wave basis sets [22] and a stress-based leastsquare fitting methodology [23]. The other theoretical constants that can be searched are the bulk moduli of LaNi 5−x Al x (0.5, 1.0) up to now [24]. Despite the numerous experimental results [18][19][20][21] and theoretical investigations [22][23][24], the experimental and theoretical data of elastic constants for LaNi 4.25 Al 0.75 have not so far been reported.…”

Section: Introductionmentioning

confidence: 99%

“…The other theoretical constants that can be searched are the bulk moduli of LaNi 5−x Al x (0.5, 1.0) up to now [24]. Despite the numerous experimental results [18][19][20][21] and theoretical investigations [22][23][24], the experimental and theoretical data of elastic constants for LaNi 4.25 Al 0.75 have not so far been reported. And the LaNi 4.25 Al 0.75 alloy is the primary tritium storage medium [25][26][27][28][29], which elastic property is important to design and improve the experiment of tritium storage.…”

Section: Introductionmentioning

confidence: 99%

First-principles study on the structure and elasticity of LaNi5 and LaNi4.25Al0.75

Zhang

Gao

Zhang

et al. 2007

Journal of Alloys and Compounds

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Relationship between compressibility and hydrogen absorption in some Haucke compounds

Cited by 9 publications

References 24 publications

Experimental and Theoretical Investigations on the Influence ofAon the Hydrogen Sorption Properties ofANi_yCompounds,A= {Y, Sm, Gd}

Experimental and Theoretical Investigations on the Influence ofAon the Hydrogen Sorption Properties ofANi_yCompounds,A= {Y, Sm, Gd}

Structural Stability of AB_y Phases in the (La,Mg)–Ni System Obtained by Density Functional Theory Calculations

First-principles study on the structure and elasticity of LaNi5 and LaNi4.25Al0.75

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Relationship between compressibility and hydrogen absorption in some Haucke compounds

Cited by 9 publications

References 24 publications

Experimental and Theoretical Investigations on the Influence ofAon the Hydrogen Sorption Properties ofANiyCompounds,A= {Y, Sm, Gd}

Experimental and Theoretical Investigations on the Influence ofAon the Hydrogen Sorption Properties ofANiyCompounds,A= {Y, Sm, Gd}

Structural Stability of ABy Phases in the (La,Mg)–Ni System Obtained by Density Functional Theory Calculations

First-principles study on the structure and elasticity of LaNi5 and LaNi4.25Al0.75

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Experimental and Theoretical Investigations on the Influence ofAon the Hydrogen Sorption Properties ofANi_yCompounds,A= {Y, Sm, Gd}

Experimental and Theoretical Investigations on the Influence ofAon the Hydrogen Sorption Properties ofANi_yCompounds,A= {Y, Sm, Gd}

Structural Stability of AB_y Phases in the (La,Mg)–Ni System Obtained by Density Functional Theory Calculations