Hydrogen absorption capabilities by transional metals.

[MTd2]

I know about the typical case of Paladium, which is said to "absorb 900x its volume in hydrogen". But this is completely vague. I'd like to know more about the theory of absorption as well as of other materials, like Nickel, Niobium and other transitional metals. Would someone, please, give me at least some online references?

 

[Drakkith]

What is vague about it? Looks to me like the structure of Paladium has "space" enough between its atoms to accommodate 900 Hydrogen atoms. Whether these actually bond with Paladium I don't know.

Edit: Here's a link for absorbtion: http://en.wikipedia.org/wiki/Absorption_(chemistry )