Manipulating the Toughness of Rocks through Electric Potentials

Metadata Updated: May 2, 2019

When rocks are stressed, electronic charge carriers are activated which are defect electrons in the oxygen anion sublattice, O[HTML_REMOVED] in a matrix of O2[HTML_REMOVED], known as positive holes. They have properties such as the ability to flow out of the stressed volume and spread into the surrounding unstressed rocks. The wave function associated with these charge carriers is highly delocalized, meaning that the spin density is distributed over hundreds of O2[HTML_REMOVED] neighbors.We conducted three sets of experiments to test the prediction that a specific quantum mechanical effect, the delocalization of the electronic wave functions associated with oxygen anions in the 1[HTML_REMOVED] valence state, has a measurable effect on fundamental properties of rocks.[HTML_REMOVED] Normally the O[HTML_REMOVED] exist in the structure of rock‐forming minerals in the form of tightly bonded O[HTML_REMOVED]pairs, called peroxy defects. We set out to measure (i) the [HTML_REMOVED]softening[HTML_REMOVED] of rocks in which peroxy defects are activated, (ii) our capability to manipulate the distribution of the electronic charge carriers, called positive holes, that arise from the delocalized O[HTML_REMOVED] states, and (iii) the volume expansion predicted to accompany the break‐up of peroxy bonds and delocalization of the wave functions. We successfully demonstrated (i) and (ii), showing a [HTML_REMOVED]softening[HTML_REMOVED] of the rocks on the order of 10‐15%. We did not yet successfully demonstrate the volume increase effect. The mechanical properties of materials, including rocks, are influenced by many factors. Most prominent among those factors are defects on different scales. They range from point defects on the scale of atoms to linear defects within grains such as dislocations, 2‐dimensional defects along grain boundaries, and larger defects such as microfractures. The many forms of imperfections can be summed up as [HTML_REMOVED]damage[HTML_REMOVED]. Damage is usually accumulative but can often be [HTML_REMOVED]repaired[HTML_REMOVED] through various annealing processes.[HTML_REMOVED] In this project we have pursued a particular form of imperfections due to point defects in the oxygen sublattice of minerals, whereby oxygen anions have changed their valence from the usual 2[HTML_REMOVED] state to 1[HTML_REMOVED]. Under certain conditions point defects that consist of pairs of O[HTML_REMOVED] become activated. As the O[HTML_REMOVED][HTML_REMOVED]O[HTML_REMOVED] bond breaks up, there is strong evidence that the wave functions associated with the O[HTML_REMOVED] become delocalized over many neighboring oxygen anion position.[HTML_REMOVED] As we show in this Report this quantum mechanical process of delocalization has a measurable effect on the mechanical properties of rocks: it makes rocks mechanically weaker and softer.

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Public: This dataset is intended for public access and use. License: U.S. Government Work

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Metadata Created Date August 1, 2018
Metadata Updated Date May 2, 2019

Metadata Source

Harvested from NASA Data.json

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Resource Type Dataset
Metadata Created Date August 1, 2018
Metadata Updated Date May 2, 2019
Publisher Space Technology Mission Directorate
Unique Identifier TECHPORT_10623
Maintainer Email
Public Access Level public
Bureau Code 026:00
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Metadata Catalog ID
Schema Version
Catalog Describedby
Datagov Dedupe Retained 20190501230127
Harvest Object Id 30b1a731-95eb-4a41-8f4c-64b870558621
Harvest Source Id 39e4ad2a-47ca-4507-8258-852babd0fd99
Harvest Source Title NASA Data.json
Data First Published 2012-01-01
Homepage URL
Data Last Modified 2018-07-19
Program Code 026:027
Source Datajson Identifier True
Source Hash a078c5a8492feafdccb278e57e97d3ff7132f96a
Source Schema Version 1.1

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