Stable and metastable structures and their energetics of asymmetric tilt grain boundaries in MgO: a simulated annealing
- PDF / 3,117,469 Bytes
- 14 Pages / 595.276 x 790.866 pts Page_size
- 53 Downloads / 164 Views
Stable and metastable structures and their energetics of asymmetric tilt grain boundaries in MgO: a simulated annealing approach T. Yokoi1,* 1 2
, Y. Kondo1, K. Ikawa1, A. Nakamura1, and K. Matsunaga1,2
Department of Materials Physics, Nagoya University, Nagoya 464-8603, Japan Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan
Received: 2 September 2020
ABSTRACT
Accepted: 21 October 2020
A simulated annealing (SA) method based on molecular dynamics is employed to reveal atomic structures of asymmetric tilt grain boundaries (ATGBs) in MgO. R5 and R13 ATGBs with the [001] tilt axis are systematically investigated. The ATGBs after SA simulations dissociate into saw-toothed nanofacets composed of multiple structural units. These nanofacets are lower in GB energy than those obtained from a c-surface method with structural optimization, demonstrating the importance of SA-based methods for obtaining low-energy structures of ATGBs. For most of the R5 ATGBs, the nanofacets consist of only structural units of R5 symmetric tilt GBs (STGBs). For the R13 ATGBs studied, their nanofacets do not consist of only R13 STGBs but always contain non-R13 structural units, which probably results from a large difference between the excess volume of R13(510) and R13(320) STGBs. It is also found that ATGBs have a larger number of metastable structures whose GB energies are close to the lowest energy structure than STGBs, due to the fact that ATGB nanofacets are more tolerant of variation in facet junction, structural units and their arrangement. Consequently, the lowest energy structures have low probabilities of being formed than metastable structures.
Ó
Springer Science+Business
Media, LLC, part of Springer Nature 2020
Introduction In crystalline materials, grain boundaries (GBs) often govern their macroscopic properties and functionalities, through changing atomic configurations and chemical compositions within a few nanometers from Handling Editor: Shen Dillon.
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10853-020-05488-4
GB planes. It has been reported that physical properties of individual GBs significantly vary with their crystallographic characteristics. For instance, increasing proportions of R3 twin GBs in metals and alloys demonstrated improved resistance to intergranular corrosion and embrittlement [1–5].
J Mater Sci
Experiments using bicrystal samples also showed that electrical conductivities [6], diffusivities [7, 8] and thermal conductivities along or across GBs strongly depend on individual GB characters [9, 10]. Although such GB properties are known to be well correlated with GB characters described with R values, they fundamentally originate from the atomic and electronic structure of GBs. To maximize beneficial effects of GBs in real polycrystalline materials, one therefore needs to fully understand the connection between the crystallographic characteristics, atomic structure and physical properties of GBs, through examining vari
Data Loading...
