The role of chemical disorder and structural freedom in radiation-induced amorphization of silicon carbide deduced from electron spectroscopy and ab initio simulations

被引：8

作者：

Leide, Alexander J. ^{[1
,3
]}

Hobbs, Linn W. ^{[1
,2
]}

Wang, Ziqiang ^{[1
]}

Chen, Di ^{[4
]}

Shao, Lin ^{[4
]}

Li, Ju ^{[1
,2
]}

机构：

[1] MIT, Dept Mat Sci & Engn, 77 Massachusetts Ave, Cambridge, MA 02139 USA

[2] MIT, Dept Nucl Sci & Engn, 77 Massachusetts Ave, Cambridge, MA USA

[3] Univ Oxford, Dept Mat, Parks Rd, Oxford OX1 3PH, England

[4] Texas A&M Univ, Dept Nucl Engn, College Stn, TX 77843 USA

来源：

JOURNAL OF NUCLEAR MATERIALS | 2019年 / 514卷

关键词：

Silicon carbide; Amorphization; Radiation damage; EELS; Ab initio simulation; Disorder; ENERGY-LOSS; TOPOLOGICAL DISORDER; MOLECULAR-DYNAMICS; ION; CRYSTALLINE; MICROSCOPY; CLUSTERS; RAMAN;

D O I：

10.1016/j.jnucmat.2018.11.036

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

Chemical disorder has previously been proposed as an explanation for the anomalously facile amorphization of silicon carbide (SiC), on the basis of topological connectivity arguments alone. In this exploratory study, "amorphous" (formally, aperiodic) SiC structures produced in ab initio molecular dynamics simulations were assessed for their connectivity topology and used to compute synthetic electron energy-loss spectra (EELS) using the ab initio real-space multiple scattering code FEFE The synthesized spectra were compared to experimental EELS spectra collected from an ion-amorphized SiC specimen. A threshold level of chemical disorder chi (expressed as the ratio of the number of carbon-carbon bonds to the number of carbon-silicon bonds) was found to be chi approximate to 0.38, above which structural relaxation resulted in formally aperiodic structures. Different disordering methodologies resulted in identifiably different aperiodic structures, as assessed by local-cluster analysis and confirmed by collecting near-edge electron energy-loss spectra (ELNES). Such structural differences are predicted to arise for SiC crystals amorphized by irradiations involving different damage mechanisms-and therefore differing disordering mechanisms-for example, when contrasting the respective amorphized products of ion irradiation, neutron irradiation, and high-energy electron irradiation. Evidence for sp(2)-hybridized carbon bonding is observed, both experimentally in the irradiated sample and in simulations, and related to connectivity topology-based models for the amorphization of silicon carbide. New information about the probable intermediate-range structures present in amorphized silicon carbide is deduced from enumeration of primitive rings and evolution of local cluster configurations during the ab initio-modelled amorphization sequences. (C) 2018 Elsevier B.V. All rights reserved.

引用

页码：299 / 310

页数：12