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Title: Chemical effects on subcritical fracture in silica from molecular dynamics simulations

Fracture toughness of silicates is reduced in aqueous environments due to water-silica interactions at the crack tip. In this paper, to investigate this effect, classical molecular dynamics (MD) simulations using the bond-order based reactive force field (ReaxFF) were used to simulate silica fracture. The chemical and mechanical aspects were separated by simulating fracture in: (a) vacuum with dynamic loading, (b) an aqueous environment with dynamic loading, and (c) an aqueous environment with static subcritical mechanical loading to track silica dissolution. The addition of water to silica fracture reduced the silica fracture toughness by ~25%, a trend consistent with experimentally reported results. Analysis of Si-O bonds in the process zone and calculations of dissipation energy associated with fracture indicated that water relaxes the entire process zone, and not just the surface. Additionally, the crack tip sharpens during fracture in water and an increased number of microscopic propagation events occur. This results in earlier fracture in systems with increasing mechanical loading in aqueous conditions, despite the lack of significant silica dissolution. Finally and therefore, the threshold for Si-O bond breakage has been lowered in the presence of water and the reduction in fracture toughness is due to structural and energetic changes inmore » the silica, rather than specific dissolution events.« less
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Geochemistry Dept.
  2. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials Dept.
Publication Date:
Report Number(s):
SAND-2018-10275J
Journal ID: ISSN 2169-9313; 668010
Grant/Contract Number:
NA0003525
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Solid Earth
Additional Journal Information:
Journal Volume: 123; Journal Issue: 11; Journal ID: ISSN 2169-9313
Publisher:
American Geophysical Union
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); SNL Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; fracture; modeling; mineral; subcritical stress; water; atomistic
OSTI Identifier:
1474087
Alternate Identifier(s):
OSTI ID: 1480904

Rimsza, Jessica M., Jones, Reese E., and Criscenti, Louise J.. Chemical effects on subcritical fracture in silica from molecular dynamics simulations. United States: N. p., Web. doi:10.1029/2018JB016120.
Rimsza, Jessica M., Jones, Reese E., & Criscenti, Louise J.. Chemical effects on subcritical fracture in silica from molecular dynamics simulations. United States. doi:10.1029/2018JB016120.
Rimsza, Jessica M., Jones, Reese E., and Criscenti, Louise J.. 2018. "Chemical effects on subcritical fracture in silica from molecular dynamics simulations". United States. doi:10.1029/2018JB016120.
@article{osti_1474087,
title = {Chemical effects on subcritical fracture in silica from molecular dynamics simulations},
author = {Rimsza, Jessica M. and Jones, Reese E. and Criscenti, Louise J.},
abstractNote = {Fracture toughness of silicates is reduced in aqueous environments due to water-silica interactions at the crack tip. In this paper, to investigate this effect, classical molecular dynamics (MD) simulations using the bond-order based reactive force field (ReaxFF) were used to simulate silica fracture. The chemical and mechanical aspects were separated by simulating fracture in: (a) vacuum with dynamic loading, (b) an aqueous environment with dynamic loading, and (c) an aqueous environment with static subcritical mechanical loading to track silica dissolution. The addition of water to silica fracture reduced the silica fracture toughness by ~25%, a trend consistent with experimentally reported results. Analysis of Si-O bonds in the process zone and calculations of dissipation energy associated with fracture indicated that water relaxes the entire process zone, and not just the surface. Additionally, the crack tip sharpens during fracture in water and an increased number of microscopic propagation events occur. This results in earlier fracture in systems with increasing mechanical loading in aqueous conditions, despite the lack of significant silica dissolution. Finally and therefore, the threshold for Si-O bond breakage has been lowered in the presence of water and the reduction in fracture toughness is due to structural and energetic changes in the silica, rather than specific dissolution events.},
doi = {10.1029/2018JB016120},
journal = {Journal of Geophysical Research. Solid Earth},
number = 11,
volume = 123,
place = {United States},
year = {2018},
month = {9}
}