The temperature dependence of the Debye-Waller factors of B2 NiAl

Debye-Waller factors in NiAl have been calculated by a direct real-space numerical simulation using a recently developed interatomic potential of the embedded-atom type. The results show that, at low temperatures, Al atoms have the larger vibration amplitude, but there is a cross-over at about 140 K above which Ni atoms have the larger amplitude. Experimental values of the Debye-Waller factors at 110 K obtained by Nuchter, Weickenmeier and Mayer in 1995 who analysed convergent-beam electron di raction patterns are in good agreement with the calculations; in particular they show the predicted greater amplitude of Al atoms. Debye-Waller factors obtained by X-ray di raction at room temperature by Georgopoulos and Cohen in 1977 are in agreement with our prediction of a cross-over between the amplitudes of Ni and Al vibrations.