  Using the scheme of Delaunay and Gabriel graphs, we analyzed the amorphous
structures of computationally created Nd-Fe alloys for several composition
ratios based on melt quench simulations with finite temperature
first-principles molecular dynamics.By the comparison of the radial
distribution functions of the whole system and those derived from the Delaunay
and Gabriel graphs, it was shown that the Gabriel graphs represent the first
nearest neighbor networks well in the examined amorphous systems. From the
Gabriel graph analyses, we examined the coordination structures of amorphous
Nd-Fe alloys statistically. We found that the ranges of distributions of
coordination numbers vary depending on the composition ratio. The angular
distributions among three adjacent atoms were also analyzed, and it was found
that the angular distributions behave differently in the Nd-rich and Fe-rich
samples. We found that the orders in the amorphous system becomes stronger as
increasing the Nd ratio, which corresponds to the appearance of crystalline
grain boundary phases at high Nd composition ratio [T. T. Sasaki et al., Acta
Mater. 115, 269-277 (2016)].
