title: A novel crystallization pathway for SiGe alloy rapid cooling.
abstract: Understanding the structural evolution of covalent systems under rapid cooling is very important to establish a comprehensive solidification theory. Herein, we conducted molecular dynamics simulations to investigate the crystallization of silicon-germanium (SiGe) alloys. It was found that during crystallization, the saturation and orientation of covalent bonds are satisfied in order, resulting in three phase transitions. The saturation is satisfied during a continuous phase transition that occurs in the super-cooled liquid state. When the orientation was satisfied at the local scale, a novel state, the critical-nuclei crystalline (CNC) phase was obtained, where the local diamond structures increase in number with time and ultimately stabilize at an average size at the critical value. Finally with a coordinated rearrangement of atoms, the orientation is satisfied globally and a stable diamond crystal is produced. For SiGe alloys this CNC phase is universal and rather stable, and the stable temperature range has a certain relationship with the cooling rate and number fraction of atoms. This novel pathway is believed to be universal for such materials including carbon. The CNC state can explain the observation that diamond can be obtained without high pressure. These findings will significantly advance the understanding of the mechanism of phase transition, particularly for covalently bonded materials.
authors.affiliation: College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China. xiaoaosky@qq.com qxie@gzu.edu.cn and School of Mathematics and Physics, Anshun University, Anshun 561000, China and Institute of New Type Optoelectronic Materials and Technology, Guiyang 550025, China.
authors.forename: Xiaotian
authors.identifier: http://orcid.org/0000-0003-1651-1772
authors.initials: X
authors.lastname: Guo
authors.affiliation: College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China. xiaoaosky@qq.com qxie@gzu.edu.cn and Institute of New Type Optoelectronic Materials and Technology, Guiyang 550025, China.
authors.forename: Zean
authors.initials: Z
authors.lastname: Tian
authors.affiliation: College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China. xiaoaosky@qq.com qxie@gzu.edu.cn and Institute of New Type Optoelectronic Materials and Technology, Guiyang 550025, China.
authors.forename: Tinghong
authors.initials: T
authors.lastname: Gao
authors.affiliation: College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China. xiaoaosky@qq.com qxie@gzu.edu.cn and Institute of New Type Optoelectronic Materials and Technology, Guiyang 550025, China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Xie
authors.affiliation: College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China. xiaoaosky@qq.com qxie@gzu.edu.cn and Institute of New Type Optoelectronic Materials and Technology, Guiyang 550025, China.
authors.forename: Yongchao
authors.initials: Y
authors.lastname: Liang
authors.affiliation: School of Physics and Electronic, Hunan University, Changsha 410082, China.
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Mo
authors.affiliation: College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China. xiaoaosky@qq.com qxie@gzu.edu.cn and School of Electronic and Information Engineering, Anshun University, Anshun 561000, China.
authors.forename: Wanjun
authors.initials: W
authors.lastname: Yan