H2 adsorbed in a two-dimensional quantum rotor state on a stepped copper surface

Physical Review B - Condensed Matter and Materials Physics

Volumn 61, Issue 24, 2000, Pages 16921-16932

  Bengtsson, L ^a   Svensson, K ^a   Hassel, M ^a   Bellman, J ^a   Persson, M ^a   Andersson, S ^a  

^a CHALMERS UNIVERSITY OF TECHNOLOGY   (Sweden)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001370274     PISSN: 01631829     EISSN: None     Source Type: Journal    
DOI: 10.1103/physrevb.61.16921     Document Type: Article

References (36)

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12. Because the total number of configurations was well above 1000, we could only afford to use eight k points in the calculations. To improve the accuracy, we made calculations with 32 k points on a coarser grid of configurations, and interpolated the energy corrections separately. This interpolation could be readily performed because the error in energy arising from the use of eight k points varies only slowly within the region of interest. To improve the convergence with respect to the k-point set size, we introduced an electronic temperature of 0.1 eV and extrapolated total energies down to zero temperature [M. J. Gillan, J. Phys.: Condens. Matter 1, 689 (1989)].
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14. The relative large internal radial force constant of the hydrogen molecule causes some numerical problems when calculating the matrix elements as central force differences, even for small displacements of 0.05 Å. These problems were handled by removing the radial component of the forces along the H-H direction, except when calculating the internal force constant.
15. Each PES was sampled using an octahedral grid of configurations, and both total energies and forces were calculated at each point. Within each "voxel" (the three-dimensional interval between neighboring grid points) a tricubic interpolation polynomial was fitted to the calculated energies and forces at the eight corners. This numerical PES has continuous derivatives, and exactly reproduces the calculated energies and forces at the grid points.
16. The interval covered was 1.3 Å
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22. 20000〉=2.3≠0.
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24. 2 when the vacuum chamber walls are kept at room temperature.
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36. A more detailed study of the inelastic cross sections of the calculated modes is required to understand why some of the calculated modes are not observed in the experiments.