Abstract
The author used a displaced Planck's distribution function as a variational one-parameter trial function to calculate some complementary bound results for the lattice thermal conductivity of Ge. An improved lower bound due to Benin (1970) is shown to be higher than the lowest bound (due to Ziman 1960) by 1.4% at 300K to 3% at 900K. Also, an upper bound due to Jensen, Smith and Wilkins (1969) is shown to be lower than its value in 'zeroth approximation' by 2.5% at 300K to 3.5% at 900K.