EXCHANGE AND THERMAL CONDUCTIVITY IN BCC HE3 CONTAINING HE4 IMPURITY

Using recent theory for solid He3, prediction of the large increase in exchange constant J and thermal resistance K-1 due to He4 impurity is attempted. Using variational methods, a large change in the He4 function but little relaxation (∼0.75%) around the He4 or change in the neighboring He3 functions is found. An increase in J by a factor of ∼1.6 only is directly predicted. If a large relaxation (∼5%) or He3 wave-function change is assumed, a large increase, but to positive J only, occurs. Direct evaluation of the change in the self-consistent force constants around the He4 fails to predict the large defect resistance. It can be predicted using a continuum model, and calculating the local compressibility change which suggests that large relaxation around the He4 may not be needed to explain K. © 1969 The American Physical Society.