THE TEMPERATURE-DEPENDENCE OF THE DEBYE-WALLER FACTORS OF B2 NIAL

Debye-Waller factors in NiAl have been calculated by a direct real-spa ce numerical simulation using a recently developed interatomic potenti al of the embedded-atom type. The results show that, at low temperatur es, 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. E xperimental values of the Debye-Waller factors at 110 K obtained by Nu chter, Weickenmeier and Mayer in 1995 who analysed convergent-beam ele ctron diffraction 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 diffraction at room temperatur e by Georgopoulos and Cohen in 1977 are in agreement with our predicti on of a cross-over between the amplitudes of Ni and Al vibrations.