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In this Letter, we have revealed the common structural behavior of metallic glasses through scrutinizing the evolution of pair distribution functions from metallic liquids to glasses and statistically analyzing pair distribution functions of 64 metallic glasses. It is found that the complex atomic configuration in metallic glasses can be interpreted globally as a combination of the spherical-periodic order and local translational symmetry. The implications of our study suggest that the glass transition could be visualized mainly as a process involving in local translational symmetry increased from the liquid to glassy states. DOI: 10.1103/PhysRevLett.105.155501 PACS numbers: 61.43.Dq, 61.43.Bn The atomic structure of metallic glasses (MGs) is a fundamental and intriguing issue in condensed-matter physics, due to its importance in understanding the glassforming mechanism and unique properties [1][2][3][4]. Many structural models have been proposed over the years, such as ''dense random packing'' of hard spheres [5] and the ''stereochemically designed '' model [6]. Although these early models significantly improved our understanding of atomic structures in MGs, especially for short-range order (SRO), they still have their own insufficiencies [7]. Recent studies confirm that the characteristics of medium-range order (MRO) clusters dictate the stability and mechanical properties of monolithic MGs [8][9][10][11], which have shed new light on our understanding of structural features at this length scale [7,[12][13][14]. By taking the earlier models further with advances in relevant experimental techniques and computational capacity, the idealized cluster packing schemes, such as efficient cluster packing on a facecentered cubic (fcc) lattice [12] and quasiequivalent clusters on an icosahedral packing [7], have been proposed and furthered our comprehension of the MRO. However, the latest finding indicated that the MRO in MGs can be described by packing of quasiequivalent clusters on a fractal network with a dimension (D f ) of 2.31 [14], implying that it is impossible to fill the real space in these amor phous solids by building blocks in a form of crystal (D f ¼ 3:0) or icosahedral-quasicrystal (D f ¼ 2:72) symmetry. The nature of atomic packing at the MRO scale or larger in MGs still remains mysterious [15].Glassy alloys are commonly considered as the state of ''frozen liquids''; nevertheless, their structure difference is obvious: A split in the second peak of the atomic-pair distribution function (PDF) curve, gðrÞ, for MGs, occurs with respect to that for liquids. Actually, the splitting of the second maximum of the gðrÞ curve into two subpeaks is recognized as a characteristic indication of amorphous solids [16], and its origin has been investigated extensively [17][18][19]. For example, Bennett proposed that the first subpeak at R 2 =R 1 ¼ ffiffiffi 3 p results from a continuum of configuration of two coplanar equilateral triangles sharing a common side, and the second one at R 3 =R 1 ¼ ffiffiffi 4 p originat...

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