Statistical Thermodynamic Analysis for Hydrogen Absorption Behaviour in a Four Monolayers (4 ML) Thick <i>bcc</i> Vanadium (110) Superlattice Being in Contact with Molybdenum Layer

Abstract

Hydrogen (H) absorption performance in a four monolayers (4 ML) thick body centered cubic (bcc) vanadium (110) interface layer being in contact with non-H absorbing molybdenum layer (Mo/V (110) superlattice) reported by Öhrmalm et al. was analyzed in terms of statistical thermodynamics. Number ª of the available interstitial sites for occupation by H atoms per V atom was determined to be 0.45 in the 4ML bcc V (110) superlattice while ª was evaluated to be 0.55 for poly-crystalline bulk bcc V lattice. With this choice of ª value, nearest neighbor HH interaction energy E(HH) in the 4ML bcc V (110) superlattice was evaluated to be zero and the extent Q of stabilization of H atom in the bcc V (110) superlattice was evaluated to be comparable to that in the bulk bcc V lattice. The evaluated reduction of ª for the 4ML bcc Mo/V (110) superlattice to 0.45 from 0.55 for the bulk bcc V lattice was concluded to be the consequence of modulation of electronic structure in the bcc V lattice in the vicinity of non-H absorbing Mo layer.

Statistical Thermodynamic Analysis for Isothermal Hydrogenation Performances of Mg<SUB>2-</SUB><SUB>y</SUB>Pr<SUB>y</SUB>Ni<SUB>4</SUB>Intermetallics (<i>y</i> = 0.6, 0.8, 1.0)

“…The detailed derivation procedure of (X) c for the condensed phase MX x might be referred to elsewhere [7,11].Anyway, the statistical thermodynamic equilibriu m condition is eventually reduced to the following Eq. (1) for the purpose of analyzing H solution under consideration [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] …”

“…)H-H interaction energy E(H-H) within a phase at respective temperature T where M might be pure metal or substitutional alloy of type A 1-y B y and Z refers to another interstitial element besides H [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. At the onset of the statistical thermodynamic analysis, number  of interstitial sites available for occupation by H atoms per M atom is chosen to fulfill the a priori assumption of constant E(H-H) within a phase by trial-and-erro r plotting ofA(x,T) ≡ RT ln {[p(H 2 )] 1/2 ·(  -x)/x} against xat an arbitrary Tto find  value yielding linear A(x,T) vs. x relationship in which slope of the plot refers to E(H-H) as explained in so me detail later in Chapter 2.…”

“…[24]), it would be more natural and straightforward to accept that change in E(X-X) of non-stoichiometric interstitial co mpound with x at a given Twould end up with phase transformation rather than being maintained in a specified crystal lattice structure. Further, set of statistical thermodynamic interaction parameter values estimated on the basis of the simp lifying a priori assumption of constant E(H-H) for extensive range of metals and alloys appear to be self-consistent among themselves [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”