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Title: Ab initio molecular dynamics simulations of low energy recoil events in ceramics

Abstract

The recent progress in the use of large-scale ab initio molecular dynamics (AIMD) to investigate low energy recoil events and determine threshold displacement energies, Ed, in ceramics is reviewed. In general, Ed shows a significant dependence on recoil direction and atom. In 3C-SiC, the minimum Ed for both C and Si atoms is found along the <100> direction, with a value of 20 and 49 eV, respectively. The results demonstrate that significant charge transfer occurs during the dynamics process, and defects can enhance charge transfer to surrounding atoms, which provides important insights into the formation of charged defects. It is found that the C vacancy is a positively charged defect, whereas the Si vacancy is in its neutral state. The minimum Ed in GaN is determined to be 17 and 39 eV for N and Ga atoms, respectively, both along the direction. The average Ed for N atoms (32.4 eV) is smaller than that for Ga atoms (73.2 eV). It is of interest to note that the N defects created along different crystallographic directions have a similar configuration (a N-N dumbbell configuration), but various configurations for Ga defects are formed. In Y2Ti2O7 prochlore, the minimum Ed for Y atoms ismore » determined to be 27 eV for a recoil along the <100> direction, 31.5 eV for Ti atoms along the <100> direction, 14.5 eV for O48f atoms along the <110> direction and 13 eV for O8b atoms along the <111> direction. The average Ed values determined are 32.7, 34.2, 14.2 and 16.1 eV for yttrium, titanium, O48f and O8b atoms, respectively. Cation interstitials at vacant 8a sites, which are generally occupied by oxygen anions, and at the bridge sites between two neighboring cations along the <010> direction are observed after low energy recoil events.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1021822
Report Number(s):
PNNL-SA-76492
34899; KC0201020
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms, 269(14):1693-1697
Additional Journal Information:
Journal Name: Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms, 269(14):1693-1697
Country of Publication:
United States
Language:
English
Subject:
Ab initio MD; Threshold displacement energy; Defects; Ceramics; Environmental Molecular Sciences Laboratory

Citation Formats

Gao, Fei, Xiao, Haiyan Y., and Weber, William J. Ab initio molecular dynamics simulations of low energy recoil events in ceramics. United States: N. p., 2011. Web. doi:10.1016/j.nimb.2011.01.131.
Gao, Fei, Xiao, Haiyan Y., & Weber, William J. Ab initio molecular dynamics simulations of low energy recoil events in ceramics. United States. doi:10.1016/j.nimb.2011.01.131.
Gao, Fei, Xiao, Haiyan Y., and Weber, William J. Fri . "Ab initio molecular dynamics simulations of low energy recoil events in ceramics". United States. doi:10.1016/j.nimb.2011.01.131.
@article{osti_1021822,
title = {Ab initio molecular dynamics simulations of low energy recoil events in ceramics},
author = {Gao, Fei and Xiao, Haiyan Y. and Weber, William J.},
abstractNote = {The recent progress in the use of large-scale ab initio molecular dynamics (AIMD) to investigate low energy recoil events and determine threshold displacement energies, Ed, in ceramics is reviewed. In general, Ed shows a significant dependence on recoil direction and atom. In 3C-SiC, the minimum Ed for both C and Si atoms is found along the <100> direction, with a value of 20 and 49 eV, respectively. The results demonstrate that significant charge transfer occurs during the dynamics process, and defects can enhance charge transfer to surrounding atoms, which provides important insights into the formation of charged defects. It is found that the C vacancy is a positively charged defect, whereas the Si vacancy is in its neutral state. The minimum Ed in GaN is determined to be 17 and 39 eV for N and Ga atoms, respectively, both along the direction. The average Ed for N atoms (32.4 eV) is smaller than that for Ga atoms (73.2 eV). It is of interest to note that the N defects created along different crystallographic directions have a similar configuration (a N-N dumbbell configuration), but various configurations for Ga defects are formed. In Y2Ti2O7 prochlore, the minimum Ed for Y atoms is determined to be 27 eV for a recoil along the <100> direction, 31.5 eV for Ti atoms along the <100> direction, 14.5 eV for O48f atoms along the <110> direction and 13 eV for O8b atoms along the <111> direction. The average Ed values determined are 32.7, 34.2, 14.2 and 16.1 eV for yttrium, titanium, O48f and O8b atoms, respectively. Cation interstitials at vacant 8a sites, which are generally occupied by oxygen anions, and at the bridge sites between two neighboring cations along the <010> direction are observed after low energy recoil events.},
doi = {10.1016/j.nimb.2011.01.131},
journal = {Nuclear Instruments and Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms, 269(14):1693-1697},
number = ,
volume = ,
place = {United States},
year = {2011},
month = {7}
}