We develop a computationally efficient algorithm for generating high-quality structures for amorphous materials exhibiting distorted octahedral coordination. The computationally costly step of equilibrating the simulated melt is relegated to a much more efficient procedure, viz., generation of a random close-packed structure, which is subsequently used to generate parent structures for octahedrally bonded amorphous solids. The sites of the so-obtained lattice are populated by atoms and vacancies according to the desired stoichiometry while allowing one to control the number of homo-nuclear and hetero-nuclear bonds and, hence, effects of the mixing entropy. The resulting parent structure is geometrically optimized using quantum-chemical force fields; by varying the extent of geometric optimization of the parent structure, one can partially control the degree of octahedrality in local coordination and the strength of secondary bonding. The present methodology is applied to the archetypal chalcogenide alloys As_xSe_1−x. We find that local coordination in these alloys interpolates between octahedral and tetrahedral bonding but in a non-obvious way; it exhibits bonding motifs that are not characteristic of either extreme. We consistently recover the first sharp diffraction peak (FSDP) in our structures and argue that the corresponding mid-range order stems from the charge density wave formed by regions housing covalent and weak, secondary interactions. The number of secondary interactions is determined by a delicate interplay between octahedrality and tetrahedrality in the covalent bonding; many of these interactions are homonuclear. The present results are consistent with the experimentally observed dependence of the FSDP on arsenic content, pressure, and temperature and its correlation with photodarkening and the Boson peak. They also suggest that the position of the FSDP can be used to infer the effective particle size relevant for the configurational equilibration in covalently bonded glassy liquids, where the identification of the effective rigid molecular unit is ambiguous.

中文翻译：

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无定形硫属元素化物作为随机八面体键合的固体：I.对第一个尖锐衍射峰，光暗化和玻色子峰的影响

我们开发了一种计算效率高的算法，可为呈现出扭曲八面体配位的非晶态材料生成高质量的结构。平衡模拟熔体的计算上昂贵的步骤被简化为效率更高的过程，即生成随机密堆积结构，随后将其用于生成八面体键合无定形固体的母体结构。根据所需的化学计量，如此获得的晶格的位点由原子和空位填充，同时允许人们控制同核键和杂核键的数量，并因此控制混合熵的作用。使用量子化学力场对得到的母体结构进行几何优化。通过改变母体结构的几何优化程度，一个人可以局部控制八面体的程度和二次键合的强度。本方法学适用于原型硫族化物合金As_X硒_{1- X}。我们发现这些合金中的局部配位在八面体和四面体键合之间插值，但是这种方式不是很明显。它展现出既非极端又非典型的结合主题。我们始终如一地恢复了结构中的第一个尖锐衍射峰（FSDP），并认为相应的中阶位阶是由包含共价和弱次级相互作用的区域形成的电荷密度波引起的。次级相互作用的数量取决于共价键合中八面体和四面体之间的微妙相互作用。这些相互作用中有许多是同核的。目前的结果与实验观察到的FSDP对砷含量，压力和温度的依赖性及其与光暗化和玻色子峰的相关性相一致。