Theoretical study of molecular hydrogen clusters

Martínez, José I.; Isla, M.; Alonso, J. A.

doi:10.1140/epjd/e2007-00095-7

Cited by 28 publications

(23 citation statements)

References 19 publications

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“…Further the vibrational corrections ͑har-monic and anharmonic͒ reduce substantially the binding energy but they are not taken into account in the present work. 19 Therefore the absolute values of E H 2 and E abs should be considered with care.…”

Section: Methods Of Calculationmentioning

confidence: 99%

First-principles study of vacancy-hydrogen interaction in Pd

et al. 2009

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Hydrogen absorption in face-centered-cubic palladium is studied from first principles, with particular focus on interaction between hydrogen atoms and vacancies, formation of hydrogen-vacancy complexes, and multiple hydrogen occupancy of a Pd vacancy. Vacancy formation energy in the presence of hydrogen, hydrogen trapping energy, and vacancy formation volume have been calculated and compared to existing experimental data. We show that a vacancy and hydrogen atoms form stable complexes. Further we have studied the process of hydrogen diffusion into the Pd vacancy. We find the energetically preferable position for hydrogen to reside in the palladium unit cell in the presence of a vacancy. The possibility of the multiple hydrogen occupancy ͑up to six hydrogen atoms͒ of a monovacancy is elucidated. This theoretical finding supports experimental indication of the appearance of superabundant vacancy complexes in palladium in the presence of hydrogen.

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Section: Methods Of Calculationmentioning

confidence: 99%

First-principles study of vacancy-hydrogen interaction in Pd

et al. 2009

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“…This solid-superfluid opposition subsequently stimulated a large number of theoretical studies of the structures of small pH 2 clusters. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Several authors claim that the small clusters with N Յ 26 are liquidlike, [4][5][6][7][8][9] others call attention to the extensive exchange between different solvation shells. 2,11 On the other hand, diffusion Monte Carlo ͑DMC͒ T = 0 calculations indicate that N = 13 and possibly 19 and 33 are magic and energetically more stable than the neighboring sizes, consistent with the clusters being solidlike.…”

Section: Introductionmentioning

confidence: 99%

Why are para-hydrogen clusters superfluid? A quantum theorem of corresponding states study

Sevryuk

Toennies

Ceperley

2010

The Journal of Chemical Physics

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The quantum theorem of corresponding states is applied to N=13 and N=26 cold quantum fluid clusters to establish where para-hydrogen clusters lie in relation to more and less quantum delocalized systems. Path integral Monte Carlo calculations of the energies, densities, radial and pair distributions, and superfluid fractions are reported at T=0.5 K for a Lennard-Jones (LJ) (12,6) potential using six different de Boer parameters including the accepted value for hydrogen. The results indicate that the hydrogen clusters are on the borderline to being a nonsuperfluid solid but that the molecules are sufficiently delocalized to be superfluid. A general phase diagram for the total and kinetic energies of LJ (12,6) clusters encompassing all sizes from N=2 to N=infinity and for the entire range of de Boer parameters is presented. Finally the limiting de Boer parameters for quantum delocalization induced unbinding ("quantum unbinding") are estimated and the new results are found to agree with previous calculations for the bulk and smaller clusters.

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“…It was reported that LDA is more suitable for describing palladium compared with the generalized gradient approximation (GGA) [11]. We thus used ultrasoft Perdew-Zunger (LDA) pseudopotentials [12] for both Pd and H. The pseudopotential of Pd also includes the semicore d state. The plane wave cut-off for the wave functions was 35 Ry and energy cut-off for the electron density was 350 Ry.…”

Section: Simulation Methodsmentioning

confidence: 99%

“…Here E mHÀv tot is the total energy of palladium hydrides with m hydrogen atoms and a vacancy in a supercell and E ðmþ2ÞHÀv tot is the total energy for the H 2 molecule in the vacancy of palladium hydride. It should be noted that we have not considered the vibrational corrections [12] in DE tot and it is known that LDA overestimates the binding energy of the H 2 molecule [7]. Fig.…”

Section: Simulation Methodsmentioning

confidence: 99%