A neutron diffraction search for non-centrosymmetric thermal oscillations in germanium and silicon

A neutron diffraction study was made of the 222 reflection of germanium and silicon between the temperatures of 25 and 500 °C. Care was taken to reduce effects of simultaneous and higher order reflections. Extinction effects were considered, as nearly perfect crystals were employed in the study. Within the sensitivity of the experiment, no 222 neutron intensity was detected. The resulting upper limit placed on β, the cubic atomic potential constant, is roughly one half of a previously suggested value.