Three-body correlations in the amorphous $Ni_{80}B_{20}$ and $Fe_{90}Zr_{10}$ alloys probed by x-ray-absorption near-edge structure calculations

X-ray-absorption near-edge structure (XANES) data have since long been expected to provide information on third- (or higher-) order correlations in materials. In the present study, three-body correlations in amorphous alloys are studied by taking advantage of XANES data. The detailed analysis of XANES results computed for amorphous alloys of the $Ni_{80}B_{20}$ and the $Fe_{90}Zr_{10}$ type provide evidence that a fraction of the atoms in the structure are likely to contribute more to the final shape of the XANES result than the other atoms. In this connection, significant contributions of electron multiple-scattering processes are responsible for the shapes. In pursuit of a structural property to link short-range geometry and multiple scattering, together with significant contrast related to the different XANES shapes, atomic triangles of defined size are introduced as a criterion to interpret XANES results. An approach introduced to display graphically the abundance of such triangles serves as a basis for further discussions. In the case of $Ni_{80}B_{20}$, the XANES results threw light on metal-metal-boron triangles with certain measures, which are likely to be of particular interest in the structure. These triangles are characterized by one metal-boron distance between 0.19 and 0.21 nm and to a smaller fraction between 0.26 and 0.29 nm, whereas the triangles’ other two sides are of average value within the ranges of the peaks of the partial pair-correlation functions. For the Zr neighborhood in $Fe_{90}Zr_{10}$ it turned out that triangles with measures deviating from average values should occur less numerously than in the discussed model