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 FEFF. The synthesized spectra were compared to experimental EELS spectra collected from an ion-amorphized SiC specimen. A threshold level of chemical disorder χ (expressed as the ratio of the number of carbon-carbon bonds to the number of carbon-silicon bonds) was found to be χ ≈ 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 sp²-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.

以前，仅根据拓扑连接性论点，就已经提出化学无序来解释碳化硅（SiC）异常容易的非晶化。在这种探索性研究中，“无定形”（正式地，非周期性）中制作的SiC结构从头分子动力学模拟，评估它们的连接拓扑结构和用于计算使用合成电子能量损失谱（EELS）从头现实空间多重散射代码FEFF。将合成光谱与从离子非晶化SiC样品收集的实验EELS光谱进行比较。发现化学无序的阈值水平χ（表示为碳-碳键数与碳-硅键数的比值）为≈≈0.38，在此之上，结构弛豫导致形式上为非周期性的结构。通过局部聚类分析评估并通过收集近边缘电子能量损失谱（ELNES）证实，不同的无序方法导致了明显不同的非周期性结构。预计这种结构差异会发生，因为通过辐照而非晶化的SiC晶体具有不同的破坏机理（因此也存在着不同的无序机理），例如，在对比离子辐照，中子辐照，和高能电子辐射。sp的证据在受辐照的样品中和在模拟中均观察到²杂化碳键合，并且与碳化硅非晶化的基于连接拓扑的模型有关。有关非晶态碳化硅中可能存在的中间范围结构的新信息，是从头算建模的非晶化序列期间，通过原始环的枚举和局部簇构型的演变得出的。