Analytic approach to the structure of amorphous iron-boron alloys

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Abstract
The structure of amorphous Fe100-xBx alloys is described by a stochastic arrangement of two structural components. compared with existing quasi-crystalline and two-phase models important improvements are introduced: (i) the heterogeneity of the system is characterised quantitatively by correlation functions for arbitrary volume fraction of the structural components; (ii) the deviation of the atomic structure in the vicinity of the boundary between the two structural components from the regular structure of the two components is taken into account by an approximation; (iii) both the atomic correlations of the single structural components and cross correlations between them are considered. The authors derive analytical expressions for partial pair distribution functions, cluster dimensions and other structural quantities. The partial pair distribution functions for Fe100-xBx are evaluated assuming the structural components to be given by BCC Fe and BCT Fe3B, and cluster dimensions are about 1 nm. The FeFe (BFe) model distribution agrees well with the experimental results of Nold et al. up to 1.3 nm (0.5 nm). The BB model curve shows a series of well separated coordination shells in contrast to the experimental one.