Einfluß der Austauschwechselwirkung auf die Wärmeleitfähigkeit von Metallen

The electron theory of metals predicts, that for T>[Theta]D the Wiedemann-Franz number L has the universal value 2,445x10^-8 (Volt/Grad)^2. For the alcali-metals Na and K the experiment value for L is nearly 10% lower. As explanation for this fact the influence of electronic exchange-forces is considered. These forces diminish the electronic heat below the Sommerfeld value. For description of the potential between two electrons the form e^2/r exp (-[my]r) is used. In the case of Na good numerical agreement with experiments is obtained if the value of [my] is taken from Landsberg's theory of X-ray emission-bands.