was changed such as to depend on the coordinates of a single hydrogen atom. The
PES is then represented in a (2 × 2) surface cell. Figure 2 shows a two dimensional
section of the resulting PES.
2.3 Quantum Dynamics
We use the Multiconfiguration Time Dependent Hartree (MCTDH) program suite
[12] to calculate vibrational eigenstates of the adsorbed particles. For the calculations on the one dimensional models for the CO/Cu(100) system, the MCTDH
version 85.2 with “exact” diagonalization using the short iterative Lanczos (SIL)
0
100
200
300
400
500
0
0.25
0.5
0.75
1
V(x) / hc cm
-1
x / L
Model 1
Model 2
Model 3
Fig. 1 Comparison of the three model potentials used to investigate the diffusion dynamics of the
CO molecule adsorbed on Cu(100). L = 255.6 pm is the bulk Cu-Cu distance [16]
x c /pm
y
c /pm
-300
-200 -100
0
100
200
300
-200
-150
-100
-50
0
50
100
150
200
Fig. 2 Section of the PES at a distance z = 90 pm of the hydrogen atom from the substrate. x c and
y c are the Cartesian coordinates. Contour lines of the PES are separated by 200 hc cm
À1 , the
smallest value indicated at the fcc sites is 50 hc cm
À1
Full Quantum Calculations of the Diffusion Rate of Adsorbates
181