The diffusion of Na adatoms on a Cu(001) surface was studied by means of quasi-elastic He atom scattering. A jump mechanism was found with an activation energy of 0.051eV, a jump length of 0.256nm, and a jump attempt frequency of 0.53THz. The adatom vibrational frequency parallel to the surface was found to be 1.23THz. The data were explained by using a realistic molecular dynamics simulation. This revealed that the attempt frequency was governed by the rate of energy exchange between adatoms and the substrate and not, as transition-state theory predicted, by the vibrational frequencies of the adatom.

J.Ellis, J.P.Toennies: Physical Review Letters, 1993, 70[14], 2118-21

 

Table 47

Diffusivity of Ni in Cu

 

Temperature (K)

D (m2/s)

613

4.67 x 10-24

622

8.32 x 10-24

637

2.10 x 10-23

659

1.38 x 10-22

685.5

4.00 x 10-22

698

1.02 x 10-21

705

1.87 x 10-21

732.5

4.28 x 10-21

735

7.15 x 10-21

750

1.68 x 10-20

766.5

3.75 x 10-20

782.5

9.86 x 10-20

801

1.44 x 10-19

849

9.25 x 10-19

872

3.05 x 10-18

921.5

1.08 x 10-17

949

2.22 x 10-17