Missing-atom structure of diamondΣ5 (001) twist grain boundary

Abstract

We carried out a combined experimental and theoretical study of grain boundaries in polycrystalline diamond, aimed at achieving the conditions in which grain boundaries are equilibrated. Raman spectra of compacted at high-pressure and high-temperature diamond powders allow us to identify signals from sp 2 -bonded atoms, in addition to a strong peak at 1332 cm −1 , corresponding to sp 3 -bonded carbon. To verify our interpretation of the experiment, 5 (001) twist grain boundaries of polycrystalline diamond were studied by means of molecular dynamics simulations using the technique proposed by von Alfthan et al. [Phys. Rev. Lett. 96, 055505 (2006)]. We find that grain-boundary (GB) configurations, from which one atom is removed, have significantly lower energy compared to those obtained with conventional techniques. These calculated GBs are highly ordered, a few monolayers thick, in agreement with experimental observations, and are primarily sp 2 bonded. This paper underlines the importance of varying the number of atoms within GBs in molecular dynamics simulations to correctly predict the GB ground-state structure.

Structure and segregation of dopant–defect complexes at grain boundaries in nanocrystalline doped ceria

“…The rationale behind studying the S5 twist boundary is that they are representative of several high-energy GBs in nanocrystalline materials, and have been examined in other materials. 54,[58][59][60] While it is impossible to study every single GB present in a nanocrystalline material, the assortment of stable GBs exploited in this work provides insight into the fundamental mechanisms at GBs accountable for controlling vital properties of nanocrystalline doped ceria. GBs optimized for nanocrystalline ceria (Fig.…”

Ab initio and atomistic simulation of local structure and defect segregation on the tilt grain boundaries in silicon

“…With this new protocol they were able to find ordered structures without coordination defects even for twist boundaries. Steneteg el al 23 later underlined the importance of this protocol in the study of Σ5 (001) twist GB in diamond, however, their lowest energy models contained coordination defects.…”