Determining the three-dimensional atomic structure of a metallic glass

Abstract

Amorphous solids such as glass are ubiquitous in our daily life and have found broad applications ranging from window glass and solar cells to telecommunications and transformer cores1,2. However, due to the lack of long-range order, the three-dimensional (3D) atomic structure of amorphous solids have thus far defied any direct experimental determination without model fitting3-13. Here, using a multi-component metallic glass as a proof-of-principle, we advance atomic electron tomography to determine the 3D atomic positions in an amorphous solid for the first time. We quantitatively characterize the short-range order (SRO) and medium-range order (MRO) of the 3D atomic arrangement. We find that although the 3D atomic packing of the SRO is geometrically disordered, some SRO connect with each other to form crystal-like networks and give rise to MRO. We identify four crystal-like MRO networks - face-centred cubic, hexagonal close-packed, body-centered cubic and simple cubic - coexisting in the sample, which show translational but no orientational order. These observations confirm that the 3D atomic structure in some parts of the sample is consistent with the efficient cluster packing model8,10-12,20. Looking forward, we anticipate this experiment will open the door to determining the 3D atomic coordinates of various amorphous solids, whose impact on non-crystalline solids may be comparable to the first 3D crystal structure solved by x-ray crystallography over a century ago14.

Revealing 3D atomic packing in liquid-like solids

“…Q4 and Q6 were used to calculate the normalized BOO parameter, defined as √Q 4 2 + Q 6 2 /√Q 4 fcc 2 + Q 6 fcc 2 , where Q 4 fcc and Q 6 fcc are the reference values of the fcc lattice. We separated crystal nuclei from amorphous structure by setting the normalized BOO parameter larger than or equal to 0.5 40 (red dashed lines in Supplementary Fig. 8a-c) .…”

“…The Q4 and Q6 values were computed based on the procedure published elsewhere 42 , where the first nearest neighbour shell distance (Fig. 1c 40 (red dashed lines in Supplementary Fig. 8a-c) .…”

“…Since its first demonstration in 2012 31 , AET has been applied to reveal a wide range of crystal defects in materials such as grain boundaries, dislocations, stacking faults, point defects, atomic ripples, bond distortion, strain tensors and chemical order/disorder in three and four dimensions 30,[32][33][34][35][36][37][38][39] . More recently, AET was used to determine the structure of a multi-component glass-forming nanoparticle and quantitatively characterize the short-and medium-range order of its 3D atomic arrangement 40 . Here we advance AET to reveal the 3D atomic structure of an amorphous Ta thin film and two amorphous Pd nanoparticles that are not metallic glasses but liquid-like solids.…”

Reversible anelastic deformation mediated by β relaxation and resulting two-step deformation in a La60Ni15Al25 metallic glass

“…The structure of metallic glasses is considered to be heterogeneous, including solidand liquid-like regions at the nanoscale, as confirmed by experiments [32][33][34] and simulations [35][36][37][38]. The interaction between the two regions before yielding, that is, the elastic back-stress applied by the solid-like regions on the liquid-like ones, leads to the anelastic response.…”