DEBYE-WALLER FACTOR DEBYE TEMPERATURE FOR NICKEL

Three Born-von Kármán lattice dynamical models obtained from neutron measurements and elastic constant measurements on Ni have been considered chiefly to calculate the Debye-Waller factor Debye temperature, θM(T). The results are compared with X-ray experimental data in the region 100°K ≤ T ≤ 520°K. Also considered are the dispersion curves, the moments of the frequency spectrum and the dependence of these moments upon the temperature. It is seen that for θM(T = 296°K), the models based on the neutron data yield 403° and 406°K, the model based on the elastic constant data yields 425°K, and the X-ray experimental value is 410°K. It appears that at high temperatures the temperature dependence of θM(T) determined using the model based on the elastic constant data agrees closely with experiment whereas the temperature dependence of θM(T) determined from thermal expansion effects alone is too small by a factor of two. However, due to experimental scatter, it is possible that only volume expansion effects are important in determining the temperature dependence of θM(T) at high temperatures. © 1969.