Dear friend Ketan Karkare

Based on your calculations, you are trying to determine the pressure at which hydrogen is absorbed by LaNi5. The pressure-temperature-composition (PCT) curve is a useful tool for understanding the hydrogen absorption properties of metal hydrides. The PCT curve shows the relationship between the pressure, temperature, and composition of the metal hydride. The theoretical calculations for the PCT curve can be obtained using thermodynamic models such as CALPHAD (Hydrogen sorption...).

The Gibbs energy for LaNi5-xAlxHy (0 ≤ x ≤ 1, 0 ≤ y ≤ 7) phase was obtained using a full CALPHAD assessment. The results showed good agreement between experimental and calculated results (Hydrogen sorption...).

It is important to note that the PCT curve is influenced by various factors such as temperature, pressure, and composition of the metal hydride. The idealized PCT curve is shown in Fig 1 (NIST-MSEL hydrogen...).

I hope this helps! Let me know if you have any more questions.

Source:

(1) Hydrogen sorption in the LaNi5-xAlx-H system (0 ≤ x ≤ 1). https://www.researchgate.net/publication/274706204_Hydrogen_sorption_in_the_LaNi5-xAlx-H_system_0_x_1.

(2) NIST-MSEL Hydrogen Storage Program: Research - Introduction. https://www.ctcms.nist.gov/hydrogen_storage/tutorials_PCT.html.

(3) Surface Properties of LaNi5 and TiFe—Future Opportunities of .... https://www.frontiersin.org/articles/10.3389/fenrg.2021.719375/full.

(4) LaNi5 related AB5 compounds: Structure, properties and applications. https://www.sciencedirect.com/science/article/pii/S0925838820345266.

Kaushik Shandilya Hello Sir ! Thanks for the suggestion, it is a great help! I was wondering if we could use the kinetics for the absorption and desorption for the theoretical calculations based on how a PCT curve should be , any recommendations ???

Hello, I would definietly start with LaNi5H6 not "7" ... in fact its even less then stoichiometric value... This may help in the calculations;)

Dear Ketan Karkare.

You may want to use Calphad databases and thermodynamic engines to calculate what you need.

You may use the thermodynamic database provided here:

Article Thermodynamic assessment of the H-La-Ni system

or here:

Article Experimental investigation and thermodynamic reassessment of...

These thermodynamic databases usually are referenced in a standard system of reference that makes them useful to be extended to other systems etc, and the compounds, their solubility, and invariant points of phase transformation used to optimize and assess thermodynamic model parameters

You then can use thermodynamic engines like:

• OpenCalphad (free): www.opencalphad.com
• PyCalphad (free): pycalphad.org
• ThermoCalc : thermocalc.com

To calculate the fraction of the phases, the composition of the phases, the equilibrium pressure of solid phases with the gas, PCI curves, and many other thermodynamic equilibrium properties and non-equilibrium properties of the system.

Please let me know if you have any questions.

Best wishes,

Ebert