Hydrogen storage of calcium atoms adsorbed on graphene: First-principles plane wave calculations

Physical Review B - Condensed Matter and Materials Physics

Volumn 79, Issue 4, 2009, Pages

  Ataca, C ^a   Akturk E ^a   Ciraci, S ^a  

^a BILKENT UNIVERSITY   (Turkey)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 60449098903     PISSN: 10980121     EISSN: 1550235X     Source Type: Journal    
DOI: 10.1103/PhysRevB.79.041406     Document Type: Article

References (15)

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10. We used the local-density approximation (LDA) since the van der Waals contributions are generally better accounted for. We also calculated binding energies by using the generalized gradient approximation (GGA). We found that the GGA binding energy for n=1 is 120 meV smaller than the LDA binding energy for H1 adsorption site. However for n=2, the binding energy becomes ∼210 meV smaller than LDA because the H2 -H2 interaction is neglected in the former. Hence GGA and LDA result in very close atom configurations. Numerical results are acquired by using VASP [G. Kresse and J. Hafner, Phys. Rev. B 47, 558 (R) (1993)]. A plane wave basis set with kinetic energy cutoff 2 | k+G | 2 /2m=900 eV has been used. The Brillouin zone has been sampled by (19×19×1) and (9×9×1) special mesh points in k space for (2×2) and (4×4) graphene cells, respectively. In the course of structure optimizations, the convergence for energy is chosen as 10-6 eV between consecutive steps, and the maximum force allowed on each atom is less than 10-2 eV/Å. The pressure on the system is kept smaller than ∼0.1 kbar per unit cell. 10.1103/PhysRevB.47.558
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