Interatomic Potentials; Aspects Which are Visible in Experimental Radial Pair Distributions
The Fourier transform of the continuous X-ray intensity — in reduced form — [(I — <f 2>)/<f>2] k yields an atomic radial pair-distribution function; f(k) is the atomic X-ray scattering factor, k = 4π sin θ/λ and 2θ, the diffraction angle. The analysis is applicable to crystalline as well as to amorphous solids. When examined in detail — and with proper regard for the effects of data termination — experiments yield information that relates closely to interatomic potentials: (i) the mean-force potential in the near-neighbor region; (ii) vibrational anharmonicity; (iii) coupled motions among near neighbors; (iv) the different scale of inter- and intramolecular vibrations; (v) deformation-caused displacements. Examples are presented in each instance, including previously unpublished data for cold worked nickel. The latter results indicate that a major effect of deformation is a displacement of some nearest neighbors to new equilibrium separations.
KeywordsInteratomic Potential Soft Sphere Intramolecular Vibration Interatomic Separation Foregoing Paragraph
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