Premium
Visualization of tetrahedral disordering in amorphous germanium through local atomic motifs
Author(s) -
Rahemtulla Aly,
Tomberli Bruno,
Kycia Stefan
Publication year - 2018
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576718012967
Subject(s) - reverse monte carlo , amorphous solid , tetrahedron , germanium , dihedral angle , crystallography , atom (system on chip) , stereographic projection , materials science , molecular physics , chemistry , crystal structure , computer science , geometry , molecule , silicon , mathematics , optoelectronics , hydrogen bond , neutron diffraction , organic chemistry , embedded system
The atomic arrangements in amorphous solids, unlike those in crystalline materials, remain elusive. The details of atom ordering are under debate even in simplistic random network models. This work presents further advancements in the local atomic motif (LAM) method, first through the introduction of an optimized alignment procedure providing a clearer image of the angular ordering of atoms in a model. Secondly, by applying stereographic projections with LAMs, the angular ordering within coordination shells can be quantified and investigated. To showcase the new capabilities, the LAM method is applied to amorphous germanium, the archetype of covalent amorphous systems. The method is shown to dissect structural details of amorphous germanium (a‐Ge) from the continuous random network (CRN) model and a reverse Monte Carlo (RMC) refined model fitted to high‐resolution X‐ray scattering measurements. The LAMs reveal well defined dihedral ordering in the second shell. The degree of dihedral ordering is observed to be coupled to bond length distances in the CRN model. This coupling is clearly not present within the RMC refined model. The LAMs reveal inclusions of third‐shell atoms occupying interstitial positions in the second shell in both models.