title: Negative expansions of interatomic distances in metallic melts.
abstract: When a material is heated, generally, it dilates. Here, we find a general trend that the average distance between a center atom and atoms in the first nearest-neighbor shell contracts for several metallic melts upon heating. Using synchrotron X-ray diffraction technique and molecular dynamics simulations, we elucidate that this anomaly is caused by the redistribution of polyhedral clusters affected by temperature. In metallic melts, the high-coordinated polyhedra are inclined to evolve into low-coordinated ones with increasing temperature. As the coordination number decreases, the average atomic distance between a center atom and atoms in the first shell of polyhedral clusters is reduced. This phenomenon is a ubiquitous feature for metallic melts consisting of various-sized polyhedra. This finding sheds light on the understanding of atomic structures and thermal behavior of disordered materials and will trigger more experimental and theoretical studies of liquids, amorphous alloys, glasses, and casting temperature effect on solidification process of crystalline materials.
authors.affiliation: International Center for New-Structured Materials and Laboratory of New-Structured Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Lou
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Wang
authors.forename: Qingping
authors.initials: Q
authors.lastname: Cao
authors.forename: Dongxian
authors.initials: D
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Tiandou
authors.initials: T
authors.lastname: Hu
authors.forename: Ho-kwang
authors.initials: HK
authors.lastname: Mao
authors.forename: Jian-Zhong
authors.initials: JZ
authors.lastname: Jiang
mesh_terms: D000497:Alloys / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D006358:Hot Temperature; D008422:Materials Testing / Q000379:methods*; D008670:Metals / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D017356:Synchrotrons; D014001:Tin / Q000737:chemistry; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry
chemical_list: D000497:Alloys; D008670:Metals; D012834:Silver; D014001:Tin; D006046:Gold; D009532:Nickel; D000535:Aluminum; D015032:Zinc
keywords: bond lengths; contraction; metal liquids