7 Electronic heat capacity in copper

From here you may load this preset , see the text of the next , or return to the preset list.

This preset compares a Debye model fit of the heat capacity with the experimental data for copper. It works fine for a while but fails at the lowest temperatures. The excess over the Debye prediction is the contribution from the electronic degrees of freedom of the conduction electrons in copper.

Estimate the limiting value of the slope at the lowest temperatures for the experimental data.

Why did we not see a corresponding tailing off for the case of lead?