Breakthrough in Amorphous Structure and Phase Transitions

Prof. Si Lan, from School of Materials Science and Engineering (SMSE), has reported a chiral medium-range order building block which can link the amorphous and crystalline states, published in the latest issue of Nature Materials with the title of "A medium-range structure motif linking amorphous and crystalline state".


NJUST is the first corresponding affiliation, and Prof. Si Lan is the first and co-corresponding author of the paper. Prof. Xun-Li Wang from the City University of Hong Kong and Prof. Yang Ren from Argonne National Laboratory are the co-corresponding authors.


"What is the nature of the glassy stat" is one of the frontier scientific problems in condensed matter physics. There are regular or semiregular polyhedral short-range (2-5 Å) ordered structures in amorphous. However, the medium-range (5-20 Åordered structure has still remained elusive. As a result, it is difficult to determine any structural link at medium-range or longer length scales between the amorphous material and its crystalline counterparts. Further compounding the issue is that an amorphous material often crystalizes into a phase of different composition, with very different underlying structural building blocks. In order to solve the above scientific problem, one needs to know whether there are structural building blocks of specific spatial length scales in amorphous matters and how to pack to form a locally ordered but long-range disordered amorphous structure.


A metastable phase with a layered periodic cubic structure was captured in a classical Pd-Ni-P bulk metallic glass system in this work. A chiral six-membered tricapped trigonal prism cluster (named 6M-TTP) with a length scale of 12.5 Å, which exists in both the cubic phase and the amorphous matrix, was revealed in Pd-Ni-P bulk metallic glasses by a suite of advanced structural characterization techniques.


The 6M-TTP can accumulate a long-range disorder structure or periodically pack to several tens of nanometers to form the cube phase. This work provides direct experimental evidence of the intrinsic structure link between amorphous and crystalline phases and demonstrates that it is the connectivity of the 6M-TTP clusters that distinguish the crystalline and amorphous phases. The results suggest that there may be some medium-range ordered structure in amorphous materials to bridge the amorphous and corresponding crystalline states (such as 6M-TTP in Pd-Ni-P metallic glass).


This work provides direct experimental evidence for the order and complexity of the multi-scale structure of amorphous materials, which will help to solve the problem of the nature of the amorphous structure and provide an essential reference for the regulation of the medium-range ordered structure of metallic glasses.


After the work of Prof. Guang Chen's group on directional solidification technology of phase transition published on Nature Materials in 2016 and the work of Prof. HaiboZeng's group on phase transition synergistic photoelectric effect on Nature Photonics in 2020, this paper is the third breakthrough in the frontier innovation field of phase transition in advanced materials published by the SMSE of NJUST. Prof. Lin Gu, professor of the Institute of Physics of the Chinese Academy of Sciences, Dr. Zhenduo Wu, professor of the City University of Hong Kong Dongguan Research Institute, and Mr. Li Zhu, Ph.D student of Nanjing University of Aeronautics and Astronautics, are the co-first authors of this paper. The other co-authors involved in this work from NJUSTare Prof. Wei Liu, Prof. Huihui Kong, Prof. Jizi Liu, the Ph.D. student from Prof. Lan's group Mr. Sinan Liu and Prof. Gang Sha.


This work was supported by the National Natural Science Foundation of China, the Outstanding Youth Fund of the Natural Science Foundation of Jiangsu Province, the Joint Laboratory of Guangdong, Hong Kong and Macao, the Hong Kong Croucher Foundation, the Hong Kong Research Foundation, and the Fundamental Research Funds for the Central Universities.

Figure 1. The direct experimental evidence revealing the medium-range ordered structure motif linking amorphous and the crystalline states.


Links

S. Lan*#, L. Zhu#, Z.D. Wu#, L. Gu#, Q.H. Zhang, H.H. Kong, J.Z. Liu, R.Y. Song, S.N. Liu, G. Sha, Y.G. Wang, Q. Liu, W. Liu, P.Y. Wang, C.-T. Liu, Y. Ren*, X.-L. Wang*, A medium-range structure motif linking amorphous and crystalline states, Nature Materials. 2021. DOI: 10.1038/s41563-021-01011-5. https://www.nature.com/articles/s41563-021-01011-5