Local Atomic Configuration of Dislocation-Accumulated Grain Boundary and Energetics of Gradual Transition from Low Angle to High Angle Grain Boundary in Pure Aluminum by First-Principles Calculations

Abstract

Dislocation-accumulated grain boundaries were systematically investigated in terms of local atomic coordinates in the vicinity of grain boundary and energetics on grain boundary evolution by first-principles calculations. Detailed numerical analyses of energy and local atomic configuration at a grain boundary with fixed misorientation angle identified the most stable configurations both for the dislocation-distinctive model and the coincident-site-lattice model with kite-shaped structural units on grain boundary planes. The energy profiles of structural optimization using both initial models indicate that the distinctive dislocations at a grain boundary can be readily converted into kite-shaped structural units without noticeable energy barrier, though they look quite different, and reverse conversion may also be realized under external stress, enabling grain boundaries functioning as dislocation sources and sinks. Systematic calculations for grain boundary with misorientation angles ranging from 5.7 to 53.1 revealed that the interaction energy between dislocation is blunted within a dislocation core region. Furthermore, the energy needed to increase the misorientation angle during severe plastic deformation is quantitatively evaluated.

Grain boundaries in nanocrystalline catalytic materials as a source of surface chemical functionality

“…This was confirmed for metallic and semiconductor nanoparticles by density functional theory (DFT) calculations (Yan et al 1998, Gao et al 2009, Yoshiya and Yoshizu 2010 and by experimental observations (Wen and Liu 1998, Yan et al 1998, Ichinose 2000, Pang and Wynblatt 2005, Sato et al 2007, Gao et al 2009). Nevertheless, there is still a lack of knowledge about the structure and chemical reactivity of atoms with low coordination located in areas where these GB emerge to the surface of materials.…”

Ceramic science of crystal defect cores

“…155)158) For that GB structures of MgO were determined by simulated annealing 185),186) One of the metrics to characterize GBs is to quantify GB energy as it quantifies the magnitude of deviations of coordination environments of atoms near GBs in terms of excess energy. 187) However, calculated values of thermal conductivity for many GBs shows a poorer correlation factor than one may expect. Rather, better correlation is found between thermal conductivities and excess volumes of GBs.…”

Defect Interactions between Screw Dislocations and Coherent Twin Boundaries in Several fcc Materials

“…It is well established that the strength and ductility of the polycrystalline metals are significantly influenced by the interaction between the dislocations and grain boundaries (GBs), among which the 3 coherent twin boundary (CTB) and dislocation interactions have been extensively investigated from experimental and computational aspects. 18) Both the strength and ductility can be remarkably increased when the CTB density rises as twinning-induced plasticity steel (TWIP). 9) This suggests that the CTB can hinder the dislocation slip, while, under certain conditions, dislocations still interact with the CTB to furnish the ductility of the nano-twinned metals.…”