The identification of glassy defects in amorphous materials is a long-standing but imperative problem which hinders our deep understanding of the structural origin of mechanical behavior in metallic glasses (MGs). Here, a combination of experiments and numerical simulations were used to reconstruct the atomic packing of MGs. Using the integration of synchrotron X-ray diffraction (XRD) datasets, ab initio molecular dynamics simulations, as well as reverse Monte Carlo simulation, we determined the three-dimensional atomic positions of a series of binary MGs CuxZr100-x (x = 50, 56, 60, 64). Then we uncovered the connection of short-range clusters as well as the nature of the medium range order (MRO). It turns out that full icosahedral tend to connect to each other forming the back bones, with dimensions positively correlated with the Cu content. By quantifying the discontinuity of full icosahedral networks, we identified the MRO defects which were found to be highly influenced by the macroscopic chemical contents. Here, the density of MRO defects is growing with the decrease of Cu contents. These results suggest the reason for the stable kinetic properties and good glass forming ability of the Cu64Zr36 system, which is rich in full icosahedral clusters <0,0,12,0> but a lack of MRO defects.

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