The strength of metals as a function of temperature is still not very
well understood, even in the case where thermal overcoming of obstacle
s by dislocations is believed not to be superimposed by other temperat
ure dependent effects? like solute atom diffusion. Our simulation calc
ulations offer a means to close some of the gaps in understanding, as
they exclude both superimposed effects of any kind as well as errors d
ue to non-ideal experimental conditions. In this contribution our resu
lts concerning the activation enthalpy and -volume for obstacles of at
omic size are presented, The simulations reveal that for equivalent co
nditions an obstacle field can well be compared to an equidistant obst
acle arrangement to be overcome. Another simplification of the activat
ion model can be done by replacing this obstacle row by a continuous o
bstacle wall without affecting the activation parameters. From this it
has to be concluded that the activation volume does not always depend
on the obstacle spacing due to first principles. A length L is introd
uced which for a concrete obstacle spacing determines the number of ob
stacles to be overcome simultaneously for thermal activation. Calculat
ions on obstacle fields show that for solute atom concentrations betwe
en 0.1% and 20%, this length L rather than the obstacle spacing contro
ls thermal activation.