Energy associated with dislocations: A calorimetric study using synthetic quartz

M. Liu, R. A. Yund, J. Tullis, L. Topor, A. Navrotsky

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

High temperature oxide melt solution calorimetry was used to study the energy associated with dislocations in quartz by comparing undeformed and deformed single crystals of synthetic quartz. Samples were deformed at 698 K, 1000-1500 MPa at a strain rate of 10-5 sec-1. Two sets of calorimetric measurements were made: (i) using a Pt capsule as a container for powdered sample, and (ii) using pellets made from sample powder without any container. For the first set of measurements, the undeformed sample with a dislocation density of enthalpy is sum of heat content H973-H295 and enthalpy of solution in molten lead borate at 973 K of 39.22 ± 1.00 kJ mol-1, while the sample deformed in the dislocation creep regime with a dislocation density of 6 × 1010 to 1 × 1011 cm-2 gave an enthalpy of 38.59 ± 0.78 kJ mol-1. For the second set of measurements the measured enthalpy of the undeformed sample was 38.87 ± 0.31 kJ mol-1, and that of a deformed sample with a dislocation density of 3 × 1010 to 1 × 1011 cm-2 was 38.24 ± 0.58 kJ mol-1. The present study and previous theoretical calculations and estimates are consistent and suggest that the energy associated with dislocations in quartz is ∼ 0.6 ± 0.6 kJ mol-1 for a dislocation density of ∼ 1011 cm-2; a precise value is difficult to determine because of the overlapping errors. These results indicate that for geologically realistic dislocation densities, the maximum excess energy due to dislocations would be ∼ 0.5 kJ mol-1 for most minerals; the exact value would depend on the Burgers vector as well as the shear modulus.

Original languageEnglish (US)
Pages (from-to)67-73
Number of pages7
JournalPhysics and Chemistry of Minerals
Volume22
Issue number2
DOIs
StatePublished - Mar 1995
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Geochemistry and Petrology

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